
Book fr J fl/A 



J 



U. S. DEPARTMENT OF AGRICULTURE, 

BUREAU OF ENTOMOLOGY— BULLETIN No. 110. 

L. O. HOWARD, Entomologist and Chief of Bureau. 



THE SPRING GRAIN-APHIS OR 
"GREEN BUG." 



BY 

F. M. WEBSTER, 

In Charge of Cereal and Forage Insect Investigations, 
AND 

W. J. PHILLIPS, 

Entomological Assistant. 



Issued September 6, 1912. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 
1912. 



/ 



U. S. DEPARTMENT OF AGRICULTURE, 

BUREAU OF ENTOMOLOGY— BULLETIN No. 110. 

L. O. HOWARD, Entomologist and Chief of Bureau. 



THE SPRING GRAIN-APHIS OR 
"GREEN BUG." £^7 

BY 

F. M. WEBSTER, 

In Charge of Cereal and Forage Insect Investigations, 
AND 

W. J. PHILLIPS, 

Entomological Assistant. 



Issued September 6, 1912. 




WASHINGTON:. 

GOVERNMENT PRINTING OFFICE. 

1912. 



£.4 






BUREAU OF ENTOMOLOGY. 

L. 0. Howard, Entomologist and Chief of Bureau. 

C L. Marlatt, Entomologist and Acting Chief in Absence of Chief. 

R. S. Clifton, Executive Assistant. 

W. F. Tastet, Chief Clerk. 

F. H. Chittenden, in charge of truck crop and stored product insect investigations. 

A. D. Hopkins, in charge of forest insect investigations. 

W. D. Hunter, in charge of southern field crop insect investigations. 

F. M. Webster, in charge of cereal and forage insect investigations. 

A. L. Quaintance, in charge of deciduous fruit insect investigations. 

E. F. Phillips, in charge of bee culture. 

D. M. Rogers, in charge of preventing spread of moths, field work. 

Rolla P. Currie, in charge of editorial work. 

Mabel Colcord, in charge of library. 

Cereal and Forage Insect Investigations. 

F. M. Webster, in charge. 

Geo. I. Reeves, W. J. Phillips, C. N. Ainslie, E. O. G. Kelly, T. D. Urbahns, 
Harry S. Smith, Geo. G. Ainslie, J. A. Hyslop, W. R. Walton, J. T. Monell, 
J. J. Davis, T. H. Parks, R. A. Vickery, V. L. Wildermuth, E. G. Smyth, 
Herbert T. Osborn, Philip Luginbill, C. W. Creel, E. J. Vosler, R. N. Wil- 
son, Vernon King, entomological assistants. 
Nettie S. Klopfer, Ellen Dashiell, preparators. 
Miriam Welles Reeves, collaborator. 
2 

ft. IMP % 

net 8 mi 



LETTER OF TRANSMITTAL. 



U. S. Department of Agriculture, 

Bureau of Entomology, 

Washington, D. C, December 28, 1911. 
Sir: I have the honor to transmit herewith for publication the 
manuscript of a bulletin on the spring grain-aphis, popularly known as 
the "green bug," by F. M. Webster and W. J. Phillips, of this bureau. 
The investigations upon which this bulletin are chiefly based began 
under a special appropriation made by Congress in the spring of 
1907. These investigations have been continued without inter- 
ruption up to and including 1911. Preliminary reports upon the 
work were published in Circulars Nos. 85 and 93. The present 
report, however, is a complete record of the entire investigation, 
including many aspects of the problem not before touched upon 
in any publication relating to this group of insects. I recommend 
the publication of this manuscript as Bulletin No 110 of the Bureau 
of Entomology. 

Respectfully, 

L. O. Howard, 
Entomologist and Chief of Bureau. 
Hon. James Wilson, 

Secretary of Agriculture. 



CONTENTS. 



Page. 

Introduction 11 

Earliest observations on the insect in America 13 

Early records in Europe 16 

Known distribution in the Eastern Hemisphere 16 

Known distribution in the Western Hemisphere 18 

The outbreak of 1890 19 

The outbreak of 1901 21 

The outbreak of 1903 21 

The outbreak of 1907 27 

Losses from depredations in 1907 39 

The situation in 1911 40 

Food plants 41 

Character of attack 44 

Viviparous development 44 

In the South 44 

In the North 49 

Rearing methods 51 

Stem mothers 58 

Description of the different instars 58 

Description of the summer forms 59 

Molting 61 

Number of molts 61 

Birth of young 63 

Number of generations per year 63 

Age at which females begin reproducing 70 

Reproductive period 71 

Longevity 72 

Fecundity of viviparous female 73 

Fecundity of wingless vs. winged females 75 

Average number of young produced daily 76 

Sexual forms 76 

Descriptions 77 

Molting 78 

Oviparous development 78 

Age at which females begin oviposition 78 

Place of oviposition .* 79 

Period of oviposition 79 

Length of life of the sexes 80 

Fecundity of oviparous forms 81 

Aberrant individuals 81 

Influence of winds on diffusion 81 

Influence of temperature on diffusion 88 

. 5 



6 THE SPRING GRAIN-APHIS OR " GREEN BUG." 

Page. 

Embryology 94 

Methods and material 95 

General description of the egg 95 

Observations 97 

Summary of embryological development 102 

Natural enemies 103 

Internal or true parasites ■ 104 

Aphidius testaceipes Cress ." 104 

Description and identity 104 

Life history 105 

Oviposition 105 

Length of period from egg to adult 106 

Effect of parasitism by Aphidius upon development of host. . 106 

Effect of parasitism by Aphidius upon fecundity of host 107 

Movement of larva within the host and manner of attaching it 

to the plant 109 

Fecundity 113 

Parthenogensis 114 

Hosts of Aphidius testaceipes 115 

Hibernation 117 

Influence of winds in the dispersion of Aphidius testaceipes 118 

Temperature influences of Aphidius 119 

Effects of wet weather on the diffusion of Aphidius 121 

Other species of Aphidius 122 

Aphelinus 122 

Notes on life history and habits of Aphelinus 124 

Secondary parasites 125 

Megorismus sp 125 

Aphidencyrtus aphidiphagus Ashm 126 

Pachyneuron sp ' 127 

Allotria sp 128 

Predaceous enemies 128 

Lady-beetles 128 

Syrphid flies 129 

Lacewing flies 132 

Cecidomyiidse 133 

Birds 135 

Miscellaneous enemies of Toxoptera 135 

Ants and their relation to Toxoptera 136 

Remedial and preventive measures 136 

Field experiments 136 

Cultural methods 139 

Artificial introduction of parasites 142 

Literature consulted .' 144 

Index ? L U5\ 



ILLUSTRATIONS. 



PLATES. 

Page. 
Plate I. Fig. 1. — Wheat field totally destroyed by the spring grain-aphis 
( Toxoptera graminum). Fig. 2. — Circular spot in wheat field where 

growing grain has been destroyed by the spring grain-aphis 32 

II. Fig. 1. — Stand on which experiments were carried out in rearing the 
spring grain-aphis. Fig. 2. — Area on grounds of the United States 
Department of Agriculture, at Washington, D. C, where the spring 
grain-aphis usually occurs on bluegrass in excessive abundance 
during summer 36 

III. Development of the embryo in the egg of Toxoptera graminum. 

Fig. 1. — Longitudinal section showing the blastoderm partly 
formed. Fig. 2. — Longitudinal section showing the thickening of 
the blastoderm about the ovarian yolk previous to invagination. 
Fig. 3. — Longitudinal section representing the germ band at the 
beginning of invagination folding inward about the ovarian yolk. 
Fig. 3a. — Section of the blastoderm. Fig. 4. — Longitudinal sec- 
tion of a more advanced stage of invagination, the germ band having 
almost closed over the ovarian yolk 100 

IV. Development of the embryo in the egg of Toxoptera graminum. 

Fig. 1. — Longitudinal section representing the somewhat cone- 
shaped germ band ready to release itself from the surface of the egg. 
Fig. 2. — Sagittal section representing the tubular germ band com- 
pletely submerged within the yolk. Fig. 3. — Transverse section of 
the germ band. Fig. 4. — Sagittal section showing the germ band 
folding and differentiating into amnion and germ band proper .... 100 
V. Development of the embryo in the egg of Toxoptera graminum. 
Fig. ] . — Sagittal section showing the germ band differentiated into 
three layers and folded almost upon itself. Fig. 2. — Surface view 
of Plate VI, figure 1. Fig. 3.— Surface view of Plate VI, figure 2. . 100 
VI. Development of the embryo in the egg of Toxoptera graminum. 
Fig. 1. — Sagittal section of the embryo, showing the segmentation. 
Fig. 2. — Sagittal section showing a much more advanced stage of 

growth than that of figure 1 100 

VII. Development of the embryo in the egg of Toxoptera graminum. 
Fig. 1. — Sagittal section showing the embryo in position to escape 
from the center of the egg. Fig. 2. — Sagittal section showing the 
embryo at the surface of the egg. Fig. 3. — Sagittal section, later 
stage of development. Fig. 4. — Sagittal section; dorsal organ im- 
mersed within the body cavity where it has begun to disintegrate. 
VIII. A lady-beetle enemy of the spring grain-aphis. Pupae of Hippodamia 
convergens attached to stem of cowpea and wheat straws in a field 

where the spring grain-aphis had .been excessively abundant 128 

IX. Fig. 1. — Brush drag used by the junior author in experiments and 
also by farmers in destroying the spring grain-aphis in the fields at 
Hobart, Okla. Fig. 2. — Roller used in experiments by the junior 
author and by farmers in experiments in destroying the spring 

grain-aphis in Oklahoma 136 

7 



8 THE SPRING GRAIN-APHIS OR " GREEN BUG." 

TEXT FIGURES. 

Page. 
Fig. 1. The spring grain-aphis (Toxoptera graminum): Winged and wingless 

viviparous females and young on wheat plant 12 

2. Map showing the locality from which the spring grain-aphis was re- 

ceived in 1882 and the two additional localities where it is probable 
that it also occurred in injurious numbers in that year; also the two 
localities where it was found in 1884 14 

3. Map showing the distribution of the spring grain-aphis in both the east- 

ern and the western hemispheres 17 

4. Map showing the known distribution of the spring grain-aphis in the 

United States and Canada 19 

5. Maps showing areas covered by outbreaks of the spring grain-aphis dur- 

ing the years 1890, 1901, 1903, and 1907 20 

6. The spring grain-aphis: Male and antenna 45 

7. The spring grain-aphis: Winged viviparous female and antenna 46 

8. The spring grain-aphis : Wingless viviparous female 47 

9. The spring grain-aphis: Oviparous female showing eggs within the abdo- 

men 50 

10. The spring grain-aphis: Hind tibia of oviparous female 50 

11. The spring grain-aphis: Eggs 51 

12. The spring grain-aphis: Young, first instar 59 

13. The spring grain-aphis: Young, second instar 59 

14. The spring grain-aphis: Pupa of winged viviparous female 60 

15. The spring grain-aphis: Shrunken and nearly spent oviparous female.. 79 

16. The spring grain-aphis: Aberrant female with both eggs and embryos in 

abdomen showing through the body wall 80 

17. The spring-grain-aphis: Aberrant female pupa which produced young. 81 

18. The spring grain-aphis: Shell of egg after young stem-mother has 

emerged 103 

19. Aphidius testaceipes, principal parasite of the spring grain-aphis: Adult 

female, antenna of male, egg ±04 

20. Aphidius testaceipes ovipositing in the body of the spring grain-aphis.. . 105 

21. Position of larva of Aphidius testaceipes in the body of wingless adult 

female of the spring grain-aphis, from 11 a. m. to 12.32£ p. m 110 

22. Position of larva of Aphidius testaceipes in the body of the spring grain- 

aphis at the beginning of the change to a yellowish color Ill 

23. Full-grown larva of Aphidius testaceipes taken from body of the spring 

grain-aphis as shown in figure 21 Ill 

24. Larva of Aphidius testaceipes spinning its cocoon in the dead body of the 

spring grain-aphis 112 

25. Larva of Aphidius testaceipes working its way prematurely from the body 

of the spring grain-aphis 112 

26. Full-grown larva of Aphidius testaceipes 112 

27. Pupa of Aphidius testaceipes immediately after pupation 113 

28. Dead "green bugs " ( Toxoptera graminum) showing exit holes of Aphidi- 

us testaceipes 113 

29. The spring grain-aphis: Winged female parasitized by Aphidius testa- 

ceipes 118 

30. Aphelinus mali: Adult and stigmal club 122 

31. Aphelinus nigritus: Adult and stigmal club 123 

32. Aphelinus semiflavus: Adult and stigmal club 124 

33. The spring grain-aphis: Dried remains from which adult Aphelinus 

nigritus has emerged 124 

34. Megorismus sp. : Male, female abdomen 126 



ILLUSTRATIONS. 9 

Page. 
Fig. 35. Aphidencyrtus aphidiphagus: Adult 127 

36. Pachyneuron sp. : Adult 127 

37. Allotria sp. : Male, female antenna 128 

38. The convergent lady-beetle {Hippodamia convergens): Adult, larva, 

pupa 129 

39. The nine-spotted lady-beetle (Coccinella 9-notata) : Adult. 129 

40.' The nine-spotted lady-beetle ( Coccinella 9-notata) : Full-grown larva. 129 

41. The spotted lady-beetle ( Megilla maculata): Adult, larva, pupa 130 

42. A South African lady-beetle, Adalia flavomaculata 130 

43. Syrphus americanus: Adult female and details of male 131 

44. Eupeodes volucris: Adult female and details of male 131 

45. Sphserophoria cylindrica: Adult female and details of male 132 

46. The golden-eyed lacewing fly (Chrysopa oculata): Adult and details, 

eggs, larvae, cocoon 133 

47. Aphidoletes sp., a cecidomyiid fly enemy of the spring grain-aphis 134 

48. Aphidoletes sp., a cecidomyiid larva which attacks the spring grain- 

aphis 135 

DIAGRAMS. 

Diagram I. Maps of the United States east of the Rocky Mountains, showing 
normal temperature and departure therefrom for the critical 

period December, 1881, to May, 1882. 15 

II. Maps of the United States east of the Rocky Mountains, showing 
normal temperature and departure therefrom for the critical 

period December, 1889, to May, 1890 21 

III. Maps of the United States east of the Rocky Mountains, showing 
normal temperature and departure therefrom for the critical 

period December, 1900, to May, 1901 25 

IV. Maps of the United States east of the Rocky Mountains, showing 
normal temperature and departure therefrom for the critical 

period December, 1902, to May, 1903 26 

V. Maps of the United States east of the Rocky Mountains, showing 
normal temperature and departure therefrom for the critical 
period December, 1906, to May, 1907 28 



THE SPRING GRAIN-APHIS OR " GREEN BUG." 



INTRODUCTION. 

Investigations of the spring grain-aphis, or "green bug" (Toxop- 
tera graminum Rond.) (fig. 1), in America were first begun by the 
senior author in the year 1884, at Oxford, Ind., where the insect was 
accidentally introduced with, or had in some obscure way gained 
access to wheat plants which had been transplanted from the open 
to rearing cages standing out of doors on a blue-grass lawn (June 6) 
and used in carrying out investigations on the greater wheat straw- 
worm (Isosoma grande Riley). At that time the insect gave no indi- 
cation of its present economic importance and for this reason was not 
then given special attention. 

In 1890, when the pest really first gave evidence of its capabilities 
as a grain destroyer over a wide range of country, the senior author 
again took up its study, gaining considerable additional knowledge 
of its habits and of the influences of temperature and season upon 
its abundance. (See Diagrams I-V.) 

The less serious outbreak of 1901 was not investigated and our 
information relative to it is derived chiefly from correspondence of 
the bureau for that year. 

The incipient outbreak of 1903 was reported from Texas by Prof. 
E. D. Sanderson, at that time State entomologist, and from South 
Carolina by correspondents of the bureau. 

The last and most disastrous outbreak of all, that of 1907, was 
investigated not only by both of the authors, but by Mr. C. N. 
Ainslie, who began his work on the species at Summers, Ark., on 
March 18, continuing the investigation almost uninterruptedly 
through the summer, working over the country from central Okla- 
homa northward to Canad-a, and returning to Washington in Sep- 
tember. The junior author spent April, May, and a portion of 
June in Oklahoma and Kansas in field investigations, returning to 
Richmond, Ind., where he was at that time located and where he 
took up a systematic study of the insect, its habits, and develop- 
ment — a study which has been continued up to the time of prepara- 
tion of this manuscript for publication. Messrs. E. O. G. Kelly and 
T. D. Urbahns spent much time in a study of the parasites; indeed; 
most of the assistants in cereal and forage insect investigations have 

11 



12 THE SPRING GRAIN-APHIS OR 

contributed more or less to our knowledge of the pest and its natural 
enemies, and throughout the following pages credit has been given 




FlG. 1. — The spring grain aphis ( Toxoptera graminum): Wheat plant showing winged and wingless 
viviparous females with their young clustered on the leaves, and a few parasitized individuals on lower 
leaves. About natural size. (Original.) 

each individual where possible to do so. For a critical, technical 
study of the parasites of the species, credit should be given Mr. J. C. 
Crawford, assistant curator, Division of Insects, U. S. National 



EARLIEST OBSERVATIONS IN AMERICA. 13 

Museum, and Mr. H. L. Viereck, expert, Bureau of Entomology, who 
are specialists in the parasitic Hymenoptera. 

During the winter of 1907-8 Congress provided the sum of $10,000 
for carrying on these investigations; otherwise this work would have 
been impossible. 

EARLIEST OBSERVATIONS ON THE INSECT IN AMERICA. 

The first examples of Toxoptera graminum to be found in America 
and identified as such were probably collected with the oats plants 
which they were destroying by Mr. H. S. Alexander, of Culpeper, 
Va., on June 15, 1882. A letter in the files of the Bureau of Ento- 
mology, written on the above date and addressed to Hon. George B. 
Loring, then Commissioner of Agriculture, stated that he, Mr. 
Alexander, was sending by that evening's mail specimens of an insect 
which had almost entirely destroyed the oats crop in his neighbor- 
hood. But he very evidently neglected to indicate on or within the 
package the name and address of the sender. Under date of June 
17, 1882, the records of the old Division of Entomology show, how- 
ever, that a package of oats or wheat plants — exactly which could 
not be determined by the person making the examination — were 
received on that date, badly infested by what was determined as 
Toxoptera graminum. As there was nothing on or within the package 
to indicate the source from which the material came, the locality 
has since remained in obscurity. Upon a recent examination of the 
old letter files, the communication of Mr. Alexander was found and a 
reply thereto by Dr. Riley, dated July 7, 1882, stating that the 
communication had been received from Mr. Alexander, but that the 
specimens referred to by him had not arrived. As the Division of 
Entomology did not have these specimens before them when Mr. 
Alexander's letter was received, or did not connect these specimens 
with his letter it was assumed that the species was the well known 
SiplionopJiora avense Fab., a name at that time applied to what is 
now called Macrosiphum granaria Buckt. Evidently the connection 
between the letter and package was never investigated, as the 
insects in the package proved to be Toxoptera. It is significant that 
of the eight communications received at the Department of Agri- 
culture about that time, from various points in Virginia and including 
also one from Maryland, all relating to the wheat louse, this one from 
Mr. Alexander is the only one not shown to have been accompanied 
by specimens, and also it was the only communication in which 
reference was made to the destruction of oats, all of the other letters 
alluding to insects found infesting wheat or rye, which were probably 
M. granaria Buckt. Without a doubt, therefore, the letter of Mr. 
Alexander refers to the package received June 17, 1882, without 



14 



name or address of the sender. A correspondent of the " Country 
Gentleman," writing over the initials G. C, from Chrisman, Rock- 
ingham County, Va., about 50 miles west of Culpeper, under date of 
June 16, 1882, makes this statement: 

Wheat looking well and promising, but there is a little green bug on it that may 
injure it. This same little green fellow is ruining the oats in this neighborhood, and 
has already destroyed them entirely in many localities. 1 

It is not at all surprising that Toxoptera and Macrosiphum should 
have been confused at that time, as the former species was yet 

unknown in the country 
and its presence could 
only be determined from 
winged individuals. In 
all of the succeeding out- 
breaks of Toxoptera it has 
been more or less difficult 
to separate the wingless 
individuals of these two 
species definitely from 
each other, even experts 
having been often at fault 
where there were only im- 
mature individuals upon 
which to base a separa- 
tion. In this connection 
Mr. B. F. White, writing 
from Mebane, N. C, Jan- 
uary 28, 1890, complain- 
ing of damage at that 
time to oats in his locality 
by Toxoptera, specimens 
of which accompanied 
his communication, stated that the same insect appeared in 1882, in 
May. So, then, it seems quite likely that, while the discovery was 
first made at Culpeper, Va., the insect occurred over a considerable 
area of country in Virginia, extending southward into northern North 
Carolina (see fig. 2; Diagram I, p. 15). 

From the foregoing it would appear that at this early date there 
was a more or less destructive outbreak of this pest in the southern 
Atlantic States. That the species was confined to this area, how- 
ever, is hardly possible, and indeed it is not beyond possibility that 
damage to oats may have extended much farther westward, though 
we have been unable to find definite proof to that effect. The all- 
important temperature influences are also indicated. 




Fig. 2.— Map showing the locality from which the spring 
grain-aphis was received in 1882 and the two additional 
localities where it is probable that it also occurred in inju- 
rious numbers in that year; also the two localities where it 
was found in 1884. (Original.) 



Cultivator and Country Gentleman, vol. 47, p. 498, June 22, 1882. 



EARLIEST OBSERVATIONS IN AMERICA. 



15 



On June 7, 1884, Mr. Albert Koebele found this species infesting 
wheat plants at Cabin John Bridge, situated in Maryland a few miles 
above Washington, and about July 1 of the same year the senior 




Diagram I. — Maps of the United States east of the Rocky Mountains, showing normal temperature, upper 
line, and departure therefrom, lower line (+, above normal, and, — , below), for the critical period 
December, 1S81, to May, 1882; above normal (+) in winter and below normal (— ) in spring being 
favorable for outbreak of spring grain-aphis. (Original.) 

author found it in one of his rearing cages, placed out of doors at 
Oxford, Ind. (see fig. 2). In the latter instance the species showed 
a preference for wheat plants over those of rye, and in September it 



16 THE SPRING GRAIN-APHIS OR " GREEN BUG." 

was common in the fields on volunteer wheat plants in the same 
locality and also about La Fayette, Ind. In some fields it was ob- 
served breeding on the young growing wheat throughout the autumn 
and early winter up to December 13. On the 30th of December it 
was still to be found alive in the fields, though not in great abundance. 

EARLY RECORDS IN EUROPE. 

The first exact knowledge we have of this insect is its occurrence 
in excessive abundance about Parma, Italy, in 1847. Five years 
later, in 1852, Rondani, who described the species during this year, 
wrote to Prof. Bertoloni under date of June 14, also from Parma, 
relative to the insect as follows: 

We have in our city an innumerable number of insects of a species of the Aphis 
genus, of Linnaeus, of the order of Hemiptera. Sometimes and in certain places the 
number of these insects flying in clouds in the air has been so great as to render them 
troublesome to people, entering the nose, eyes, and even the mouth, when one can 
not think how to protect oneself from them. 

Elsewhere in this letter Rondani stated that he had never been 
able to find it on any but graminaceous plants, where it nestled on 
the leaves. In commenting on this letter of Rondani, Prof. Bertoloni 
took occasion to say that " innumerable specimens of the Aphis 
graminum Rondani are seen in the streets of the city of Bologna, and 
these have several times entered my nose and eyes when passing 
rapidly along the canal of Reno." 

KNOWN DISTRIBUTION IN THE EASTERN HEMISPHERE. 

Besides these occurrences in Italy and Hungary (see fig. 3), in 1884 
Dr. G. Horvath records an attack on oats in central Hungary, which 
took place in June, 1883, and 10 years later, in 1894, Prof. Carl Sajo 
records a second outbreak among growing oats, also in Hungary. 

Schouteden, in 1906, records the species from Belgium, but gives 
no further data except that it affects the Graminacese. 

Under date of October 7, 1907, Mr. H. Neethling, chief of the 
horticultural and biological division, department of agriculture, 
Bloemfontein, Orange River Colony, South Africa, in a letter ad- 
dressed to the United States Department of Agriculture, stated that 
the wheat aphis was one of the greatest scourges with which the 
farmers of his colony had to contend, nearly the whole crop having 
been destroyed by it for several consecutive seasons. Again, under 
date of September 28, 1908, the same gentleman stated that the pest 
had been particularly active that season, it being estimated that 
more than 50 per cent of the entire wheat crop of the colony had 
been destroyed by its ravages. This latter communication was 
accompanied by specimens of Toxoptera graminum as well as a small 



DISTRIBUTION. 



17 




26675°— Bull. 110—12 



18 

hymenopterous parasite, ApTiidius sp., and larvae and adults of a 
coccinellid, Adalia flavomaculata De G., both of which were observed 
destroying the aphidids. Under date of October 1, 1910, Mr. C. P. 
v. d. Merwl, assistant biologist of the same department, stated that 
another outbreak of the pest had taken place that spring and con- 
siderable damage had been done. In this communication the state- 
ment was made that the writer had personal knowledge of the 
occurrence of the species during the past 20 years, and that farmers 
had stated that they had always known of its occurrence in that 
country. It had, however, become seriously destructive during 
recent years and at that time farmers were being forced to give up 
growing wheat extensively on account of its ravages. 

In the Agricultural Journal of India 1 Mr. H. Maxwell-Lefroy, 
government entomologist of British India, stated that the wheat 
aphis (Toxoptera graminum) seeks shelter in the depths of the grass 
roots; in different ways insects adapt themselves, but these had 
probably done it gradually, moving in from cooler to hotter areas 
step by step. From the illustration of this insect accompanying this 
statement and from specimens later submitted by Mr. Maxwell- 
Lefroy, it has been found impossible to determine the species involved 
as Toxoptera graminum. 

On November 25, 1910, Mr. William Sewall, of Njoro, British East 
Africa, called at the office of this bureau to complain of the ravages 
of a green louse or fly which attacked and destroyed wheat on his 
farm in the above-named locality, situated almost directly on the 
equator in a prairie-like country at an elevation of 7,000 feet above 
sea level. A communication was received from Mr. Sewall bearing 
date of August 22, 1911, accompanied by specimens, in which he 
stated that the ravages now extend over an area of 700 acres. He 
also stated that his neighbor, Lord Delamere, who had not been 
troubled previously, experienced severe losses over an area of about 
4,000 acres. The specimens accompanying Mr. Sewall's letter have 
been determined as Toxoptera graminum by Mr. J. T. Monell. 

With these records of the known and probable distribution of 
Toxoptera graminum, it does not seem improbable that if the minute 
insects of the family Aphididse were carefully studied this species 
would be found generally diffused throughout the temperate and 
tropical regions of the world. 

KNOWN DISTRIBUTION IN THE WESTERN HEMISPHERE. 

With reference to the distribution of this insect in the Western 
Hemisphere (see fig. 4), it can be said that it has only been studied in 
the United States. Its occurrence in western Canada is well established. 
On the south it is known along the Mexican border from the Gulf of 

« "Imported insect pests." Agricultural Journal of India, vol. 3, part 3, pp. 243-244, July, 1908. 



THE OUTBREAK OF 1890. 



19 



Mexico almost to the Pacific Ocean. It has not actually been found 
in Mexico and no one has searched for it there. Wheat in Mexico is 
said to have been injured by a "green louse/' and it is reasonable to 
suppose that the insect may occur far to the southward of its present 
known range of distribution. Its entire absence from eastern Canada 
and northeastern United States, except in eastern Massachusetts near 
Boston, where it seems to have been found by "Mr. Paul Hay hurst in 
September, 1908, will be noted. 

THE OUTBREAK OF 1890. 

(Fig. 5, p. 20; Diagram II, p. 21.) 

Up to the year 1890 in this country the very destructive nature of 
this insect had not yet become apparent ; hence it had not received the 
close attention that, as we now understand, it justly deserves. 




Fig. 4. — Map showing the known distribution of the spring grain-aphis in the United States and Canada. 

(Original.) 

While the senior author was and had been engaged in grain-insect 
investigations in Indiana during the six years following its discovery 
by him at Oxford, the species was not looked upon as one of those 
deserving especial attention; therefore from 1884 to 1889 no notes 
were made upon it, and no references to it are to be found in the 
correspondence of the Division of Entomology. Mr. J. T. Monell, 
now of this bureau, however, has specimens in his collection from 
Illinois, taken in 1886. 

During November and December, 1889, the insect was again 
observed in such abundance in fields of young wheat about Lafayette, 
Ind., as to attract the attention of the senior author, who found it 
repeatedly oh young wheat in the fields during the entire winter. 
The influences of mild or high temperatures during winter, especially 



20 



THE SPRING GRAIN-APHIS OR " GREEN BUG." 



in the South, and low temperatures during spring months were 
carefully observed and set forth in a report published later. 1 

As early as the middle of January, 1890, it was reported by Mr. 
P. C. Newkirk as killing the young wheat about Jalapa, Tenn., and 
on the 26th of the same month Mr. B. F. White, of Mebane, N. C, 
reported it as ruining both wheat and oats in his neighborhood. Mr. 
J. L. Fooks, writing on the same date from Era, Tex., stated that the 
insect had played sad havoc with the wheat in his neighborhood, 
while April 7 Mr. D. J. Eddleman, Denton, Tex., complained of the 
pest destroying the wheat. Writing in 1901 Mr. H. K. Jones, Valley 
View, Tex., stated that the insect appeared there about 10 years pre- 




Fig. 5.— Maps showing areas covered by outbreaks of the spring grain-aphis during the years 1890, 1901, 

1903, and 1907. (Original.) 

vious and killed about all the wheat in the county. From tins and 
other correspondence, accompanied by specimens, it seems that 
wheat in Cooke, Grayson, Collins, Denton, and Wilbarger counties, 
Tex., was more or less damaged by this pest. 2 No reports are at hand 
showing injuries to wheat or oats in what was at that time Oklahoma 
and Indian Territories, for the reason that little of either of these 
grains was at that time grown. But we now know that grains were 
not essential to its presence in that country. 

In Missouri the situation was more acute and strongly indicates 
that the pest was present in southeastern Kansas and northern 
Arkansas. According to Mr. Monell's notes, the pest completely 

» Insect Life, vol. 4, pp 3 245-248, 1892; Bui. 22, Div. Ent., U. S. Dept. Agr., pp. 64-70, 1890; Yearbook 
U.S. Dept. Agr. for 1907, pp. 239-241. 
» Insect Life, vol. 3, p. 75. 



THE OUTBREAK OF 1890, 



21 



destroyed a field of 60 acres of oats belonging to Hon. Roland Hazard 
at Mine Le Motte, situated about 100 miles south of St. Louis, Mo., 




Diagram II. — Maps of the United States east of the Rocky Mountains, showing normal temperature, 
upper line, and departure therefrom, lower line (+, above normal, and — , below normal), for the 
critical period December, 1889, to May, 1890; above normal ( + ) in winter and below normal (— ) in 
spring being favorable for outbreak of spring grain-aphis. (Original.) 

the observations being made June 10, 1890. In Missouri the situa- 
tion appears to have been pretty clearly set forth by Colman's Rural 
World, then the leading agricultural paper of the Southwest. In the 



22 THE SPRING GRAIN-APHIS OR u GREEN BUG. M 

issue of that publication for June 12, 1890, the following statement 
is made: 

The oat crop in the vicinity of St. Louis and probably extending a hundred miles 
in every direction is being completely destroyed this season by an aphis, commonly 
called, we believe, the Texas louse. The oat fields look brown and bare, this little 
green insect sucking the juices and sapping the vitality of the plant. It increases 
with amazing rapidity, fully as rapidly, we judge, as the hop louse, swarming in every 
direction and carrying destruction in its path. The only thing they seem to feed 
upon is the oat. 

In the issue of the same publication for June 19, a week later, the 
following statement is made : 

The oat crop this season will be almost a total failure in St. Louis County. Hundreds 
of acres have been totally destroyed by the aphis, or plant louse, the depredations of 
which have been so widespread and effective that only a very small per cent of the 
crop will mature. Hundreds of farmers have despaired of the crop entirely, and have 
plowed up their oat fields and planted corn instead. 

The Weather Crop Bulletin of the Missouri State Board of Agri- 
culture for the week ending July 4, 1890, gives the following estimates 
of the oats crop throughout the State. Northeastern Missouri, 63 per 
cent; northwestern Missouri, 70 per cent; southeastern Missouri, 25 
per cent; central Missouri, 30 per cent; southwestern Missouri, 54 
per cent. As another writer describes it, the damage was most serious 
south of a line drawn diagonally across the State from the northeast 
to the southwest corner.* 

The statement made in Colman's Rural World to the effect that the 
oats crop within a radius of a hundred miles of St. Louis had been 
completely destroyed by the oats aphis or 'Texas louse " would include 
within this radius territory nearly half way across southern Illinois. 
Mr. B. F. Johnson, of Champaign, 111., an agricultural writer, who 
appears to have traveled over the country quite extensively and 
observed the situation closely, writing to the Country Gentleman 
under date of June 24, sized up the situation as follows: 

For some weeks after it was seen above ground, the oat crop looked well and promised 
well, and this continued to the first or about that date in June. Since then oats have 
been going behind hand, with the threat now over them that all the crop has been 
more or less seriously reduced in yield and a considerable portion will be lost. In fact, 
the oat aphis, after ruining the oat crop south, has appeared on the black soil in force 
and nothing less than many and heavy rains will arrest his progress. As before reported, 
the dry weather in May favored a light growth of straw, as in 1887, and hopes were 
entertained that long heads of sound grain would result. Such would have been the 
case had not the aphis appeared and sucked a part of the life-blood of the plants. 
The present appearance of a majority of oat fields — the acreage on the black soil coun- 
ties is an enormous one — is rather uneven as to growth, color, and measure of develop- 
ment, a part of which is owing to the greater or less fertility of the soil, but chiefly to 
the depredations of the aphis, that takes the weakest plants growing on the thinnest 
land. 

In the issue of August 14 of the same publication, Mr. John M. 
Stahl, of Adams County, 111., states that in western Illinois the only 



THE OUTBREAK OF 1890. 23 

cause of the failure of the oats crop recognized was the green louse. 
Directly upon this point his statements were as follows : 

We never had a better prospect for oats until the green louse began its work. Some 
fields were not attacked by the louse, though it infested surrounding fields. From the 
fields not attacked by it there was a splendid yield of oats; while, of course, the other 
fields yield scarcely anything. In every township there were a few fields that were 
not attacked by the green louse and that made a good yield. The fact that those fields 
not attacked by the green louse invariably made a good yield, while those that were 
attacked made a poor yield, is proof that in this part of the State, at least, the green 
louse was the prime cause of the failure. 

This feature of the apparent immunity of some fields from attack 
while others adjacent were destroyed has since been observed again 
and again, especially along the borders of a serious invasion, which 
was precisely the stuation in western Illinois at the time indicated by 
Mr. Stahl. In Indiana the senior author investigated the outbreak 
personally, and while the pest was present as far north as Lafayette, 
there was little if any damage from its attacks north of Indianapolis. 
In the neighborhood of Franklin on June 25 many fields were badly 
damaged, but the injury was much more severe to the southward 
and at New Harmony, Ind., on June 11, the oats crop was ruined. 
The same was to be said of the country across the Wabash River in 
Illinois. While both Toxoptera and Siphonophora were present 
in most cases the former largely outnumbered the latter and there 
was no difficulty in properly crediting the destruction to Toxoptera. 

The occurrence of this insect in southern Ohio was greatly obscured 
owing to the fact that it was, as elsewhere, confused with Macrosiphum 
granaria Buct. Clarence M. Weed, writing for the Ohio Farmer (see 
issue of July 12, 1890), states that in Ohio the grain plant louse had 
been reported from Pickaway, Clermont, Butler, and Franklin coun- 
ties. It seems, however, that in Clermont County, according to Mr. 
Ed. C. Ely, the plant lice were at work as early as May 30. 

In a later issue of the same paper, July 19, 1890, Hon. Abner L. 
Frazer, of Clermont County, Ohio, stated that the aphidids were 
very numerous in his fields on June 9. While it is impossible to say 
with absolute certainty that all damage was due to Toxoptera, 
nevertheless Waldo F. Brown, writing from Butler County 1 on 
June 19, says: 

Oats are in a critical condition. The leaves have turned red. It has not the 
appearance of rust, looking more like the firing of a plant in dry weather, and I should 
not wonder if the crop proved a total failure. 

In both Illinois and Missouri the aphidid causing the damage was 
termed the " Texas louse, " and wherever a technical name for it 
was used at all it was called Siplionopliora avense Fabr. Because 
Toxoptera was at that time but little known, and owing to the 

i Country Gentleman, June 26, 1890, p. 506. 



24 THE SPRING GRAIN-APHIS OR " GREEN BUG.'' 

extreme difficulty in separating its young and its wingless adults 
from those of other species, it would seem that more or less damage 
to the oats crop might be with justice accredited to Toxoptera in 
Butler, Miami, and Clermont counties in extreme southern Ohio. 

THE OUTBREAK OP 1901. 

(Fig. 5, p. 20; Diagram III, p. 25.) 

The outbreak of 1901 was less extensive than that of 1890. Little 
damage was reported south of Waco, Tex., but from this point 
northward wheat was more or less injured, and oats were destroyed 
to the northward into what was at that time Oklahoma and Indian 
Territories. The farthest point to northeast at which damage was 
reported, with specimens of the depredator, was Saratoga, in extreme 
southwestern Missouri. The specimens accompanying correspond- 
ence from Texas and Oklahoma gave ample proof of the identity 
of the destroyer, which in Texas alone ruined grain to the extent 
of several million dollars. In central Texas the ravages of the pest 
began to attract attention early in March, while the report from 
Missouri came under date of April 30. It will be noticed that the 
direction taken by this invasion followed very closely that of 1890 
(see fig. 5), beginning, however, farther south in Texas, not extending 
so far to the northeast, and dying out, as it were, earlier in the 
season. These phenomena will be explained farther on under 
meteorological influences. 

THE OUTBREAK OF 1903. 

(Fig. 5, p. 20; Diagram IV, p. 26.) 

As foreshadowing the impending outbreak of 1903, as early as 
November 26, 1902, Mr. J. F. Ordman, writing from Windthorst, 
Tex., complained to this bureau of the ravages of the green louse, 
stating that it had destroyed several small areas in his wheat field 
and that it was reported generally prevalent in his neighborhood. 
This outbreak was, however, an incipient one and resulted in little 
injury, the seriously infested areas being confined to northern Texas, 
exclusive of the " Panhandle," with possibly the country in the 
then Oklahoma and Indian Territories bordering the Red River, 
and in South Carolina. While the outbreak was thus limited in 
area, the natural enemies of the pest in the West evidently fell far 
short of completely subjugating it. In March, 1904, Prof. E. D. 
Sanderson and Mr. E. C. Sanborn found it in Grayson County, Tex., 
sufficiently abundant to work serious injury in the fields of young 
wheat and oats, in some cases the destruction of the growing grain 



THE OUTBREAK OF 1903. 



25 



being complete. The same gentlemen reported the pest present in 
limited numbers during the spring of 1904 in Collin, Hunt, and 




Diagram DX— Map of the United States east of the Rocky Mountains, showing normal temperature, 
upper line, and departure therefrom, lower line (+, above normal, and — , below), for the critical period 
December, 1900, to May, 1901; above normal ( + ) in winter and below normal (— ) in spring being 
favorable for outbreak of spring grain-aphis. (Original.) 

Travis counties. This year, however, the parasites evidently did 
more effective service, as at Whitewright, Grayson County, Tex., on 
March 10, 1904, Mr. Sanborn found that 60 per cent of the Toxoptera 



26 



THE SPRING GRAIN-APHIS OR " GREEN BUG." 



in some oats fields were parasitized. The junior author spent some 
time in northern Texas during November and December, 1904, 




Diagram IV.— Map of the United States east of the Rocky Mountains, showing normal temperature, 
upper line, and departure therefrom, lower line (+, above normal, and — , below), for the critical period 
December, 1902, to May, 1903; above normal (+) in winter and below normal (— ) in spring being 
favorable for outbreak of spring grain-aphis. (Original.) 

investigating insects in the fields of wheat and oats without finding 
the pest. He was not looking for this species particularly, and it 
was doubtless still present in very limited numbers. 



THE SPRING GRAIN-APHIS OR " GREEN BUG. 27 

THE OUTBREAK OF 1907. 

(Fig. 5, p. 20; Diagram V, p. 28.) 

The outbreak of 1907 was by far the most serious and widespread 
that has occurred in the United States up to the present time. Start- 
ing in east-central Texas, the invasion swept northward and east- 
ward, covering a somewhat fan-shaped area, through Oklahoma, 
Kansas, northwestern Arkansas, Missouri, and across Illinois to 
within 60 miles of Chicago. Though possibly not doing so much 
damage in the Ohio Valley as in 1890, it extended westward through 
Oklahoma and Kansas into southeastern Colorado. While not 
especially injurious to oats and not at all to wheat in the States of 
Nebraska, Iowa, Minnesota or the Dakotas, the late Dr. James 
Fletcher states that in Canada it actually did some damage in Sas- 
katchewan. Less damage was probably done in Indiana and Ohio 
than in 1890, though the ravaged area in general followed the ground 
covered by the previous outbreaks; in this latter case the northeastern 
terminus of the seriously ravaged area appeared to be confined more 
closely to the upper Mississippi River and Illinois River valleys than to 
that of the Ohio River, thus sweeping more broadly to the northward. 
On the Atlantic coast fall oats were destroyed or badly injured in 
South Carolina, and both wheat and oats in western North Carolina. 
In Virginia, Kentucky, and Tennessee neither grain was, as a rule, 
seriously damaged. The areas shown in figure 5 indicate all injury, 
even though slight, in occasional and widely separated fields. In 
the valleys of the upper Missouri River and the Red River of the 
North there was little or no injury, and it seems doubtful if the pest 
occurred in that section prior to this outbreak. 

Forebodings of trouble from this pest came as early as November 
and December, 1906. According to copies of Mr. Sanborn's notes, 
as placed at our disposal by Prof. A. F. Conradi, the species was sent 
to the Texas experiment station from Howe, Grayson County, Tex., 
where it occurred on oats, as early as November 14, 1906, and one 
day earlier from Allen, Collin County, of the same State, where it 
was present in great numbers attacking volunteer oats plants. On 
December 22, 1906, it was sufficiently abundant about Piano, Collin 
County, Tex., to destroy oats in patches in the fields, its natural 
enemies at the time being in a dormant condition because the tem- 
perature had not reached and remained at a degree that would 
render them active. During January and February, 1907, these 
conditions continued, the Toxoptera breeding and spreading unre- 
strained by its enemies, so that the area over which it was becoming 
destructive continually increased. 

Rumors of injuries by this pest came to us early in January, 1907, 
from east-central Texas, where the " green bugs" were reported to 
Mr. W. D. Hunter, in charge of cotton boll weevil investigations of 



28 



THE SPRING GRAIN-APHIS OR ' 4 GREEN BUG. 



this bureau, as attacking fall oats. During this month in Texas east 
of a line drawn from near Gainesville through Abilene and San 




Diagram V.— Map of the United States east of the Rocky Mountains, showing normal temperature, 
upper line, and departure therefrom, lower line (+, above normal, and — , below), for the critical period 
December, 1906, to May, 1907; above normal (+) in winter and below normal (-) in spring being 
favorable for outbreak of spring grain-aphis. (Original.) 

Antonio to Galveston the temperature was 9° F., above the normal. 
Within this area was a smaller one, the boundaries of which may be 
indicated by a line drawn from Texarkana to Fort Worth, Waco, and 



THE OUTBREAK OF 1907. 29 

Joaquin. Over this latter area the temperature for the same month 
was 12° F. above the normal, and within this latter area the pest 
first began its work of destruction. 

For reasons to be explained later in their proper place, the spread of 
the pest was much more rapid to the north and northeast from north- 
central Texas than it was in the opposite direction. In March the 
pest was found generally present about San Antonio, Kerrville, 
Menardville, and New Braunfels, of that State, but because of the 
small acreage of grain grown in that section the damage was not 
serious. Indeed, the same may be said of the country west of a line 
drawn from western Wilbarger County to the Brazos River at Round 
Timber, Baylor County, and west of the Brazos to and except about 
Waco. East and north of this the damage ranged from serious to 
total ruin. 

As early as March 6 it was also reported to the bureau as destroying 
wheat in the vicinity of Summers, northwestern Arkansas. This 
was probably due to local causes, uninfluenced by invasions of 
swarms of winged viviparous females that were being continually 
swept from off the more disastrously affected country to the southwest 
and drifting toward the northeast. Mr. C. N. Ainslie was instructed 
to proceed from Washington, D. C, to this part of the country, where 
he arrived on March 16. On March 15 the Texas Grain Dealers' 
Association, through its secretary, Mr. H. B. Dorsey, made an appeal 
to the chief of this bureau for aid in devising means for destroying 
the pest and curtailing or preventing its ravages. In response to 
this appeal the junior author was dispatched to Fort Worth, Tex., 
arriving there on March 26. The situation here was found to be most 
serious. Hundreds of acres of both wheat and oats had been wiped 
out of existence; in many cases fields were observed where it was 
impossible to find a living plant, and as a rule numbers of such fields 
were being plowed and prepared for other crops. Plate I, figure 1, 
shows a field entirely destroyed. The weather at this time was hot 
and dry and Toxoptera appeared to have been entirely overcome by 
its natural enemies. 

On March 25, 1907, a telegram was received from the Roosevelt 
Grain Elevator Co., of Hobart, Okla., reporting serious attacks from 
Toxoptera and appealing to the Secretary of Agriculture for assist- 
ance. The junior author was at once instructed to proceed to Hobart, 
where he arrived April 1, remaining until April 5. This point ap- 
peared to be on the western border of serious injuries by the pest, and 
the situation was therefore not so grave as in Texas. From the 
junior author's observations it appeared that much of the damage 
that was being done was caused by insects which had drifted into the 
fields and not from individuals originating therein. This was evi- 
denced by the fact that in wheat fields where a part had been sown 



30 THE SPRING GRAIN-APHIS OR 

early and the remainder later in the season the latest sown was very 
much more seriously damaged than that sown earlier. About the 
only portions of the early-sown part of the field to suffer serious 
injury were on the poorest soil. In short, the Toxoptera was found 
to be working its greatest damage in late sown or pastured wheat 
fields and among the young oats. Natural enemies were busily at 
work and apparently fast overcoming the pest. 

In the meantime Mr. Ainslie had found the pest destroying wheat 
in spots in the wheat fields about Fayetteville and Summers, Ark., 
March 16 to 20, as well as at Chandler, Okla., March 24, and at Guth- 
rie, Okla., on March 25. Near the latter place large circles were 
observed in the otherwise green fields of wheat. In the center of 
these circles the red soil was exposed by reason of the killing of the 
wheat plants, and these exposed circular areas were bordered by a 
band or girdle of yellow half-dead wheat plants, where the Toxoptera 
were most abundant. (See PL I, fig. 2.) In another field in this 
vicinity there was a stack of oats straw of the previous year, and from 
this stack a dead area extended at least 100 feet to the south. This 
area was nearly circular, with the stack almost in the center of the 
circumference. Near and surrounding the stack was an area of dead 
volunteer oats, and beyond this a stretch of bare ground indicated 
where wheat had once stood. From people occupying a house near 
by something was learned of the previous history of this straw stack 
from which Mr. Ainslie determined that volunteer oats had sprung 
up after thrashing in 1906; these oats turned brown soon after, 
causing some wonder among farmers, and during the winter the plants 
died. The trouble spread to the wheat adjoining and here the wheat 
plants died early in the spring. There was here seemingly a repetition 
of the conditions in the fields about Summers, Ark., where Toxoptera 
infesting volunteer oats extended its destruction from these to the 
wheat near by. 

On March 26, between Guthrie and Kingfisher, Okla., Mr. Ainslie 
observed that the dead spots in the wheat fields were a striking feature 
of the landscape, for in the sunshine the bright green of the young 
grain made a striking contrast with the yellow-rimmed red circles 
where the Toxoptera had destroyed the wheat. Occasionally a field 
was free from these areas, but more of them were frightfully spotted 
in this manner. A field of wheat that was pastured more closely than 
most grain fields lay in the edge of Kingfisher and showed the attack 
of the Toxoptera worse than in adjoining grain. On March 27, at 
Kingfisher, Toxoptera was flying by the millions, the air being full of 
the migrants, and farmers who drove to town were covered on the 
windward side to their annoyance. The aphides seemed for the most 
part to fly low, but the wind hurried them at such a rapid rate that 
they might easily have been invisible when higher in the air. On the 



THE OUTBREAK OF 1907. 31 

following day large numbers of Toxoptera were on the wing, always 
moving north. In a field of oats, sown in February, the plants had 
hitherto been very thrifty, but at this time in a great many of the 
drill rows the plants were about dead for a space of 8 or 10 feet, and 
in case of later sown fields the plants were all fast dying under the 
attack. There was becoming gradually apparent a fact of consider- 
able importance regarding the relative number of winged forms in 
the fields. In oats fields where the food was succulent and good it 
was difficult to find a single pupa, while in older and less succulent 
wheat, perhaps within a yard of the oats, pupae would form 75 or 80 
per cent of the population of the blades. This was afterwards verified 
repeatedly by observation and by actual counting; indeed, through- 
out the entire spring this fact seemed to be substantiated. 

From March 31 to April 3 Mr. Ainslie carefully examined fields of 
wheat and oats in the vicinity of Wellington, Kans. He found wheat 
fields invariably evenly infested with Toxoptera though nowhere in 
any great numbers. Many of these were winged adults, indicating 
that they were migrants, and the young about them clearly evidenced 
a recent invasion. No dead areas were observed in the fields north 
of Pond Creek, Okla., but between Kingfisher and this point the 
circular dead spots were plainly in evidence. These dead areas, 
(PI. I, fig. 2), from their regularity in the field, plainly indicated the 
rows of oats shocks of the fall previous and were clearly to be seen 
where the oats had been shocked and allowed to stand through a period 
of wet weather. This generally produced a vigorous growth of 
volunteer oats when the shocks were finally stacked or removed, 
and in this young grain the Toxoptera seem to have had an early 
start. In some cases it was easily possible to observe these spots 
all over a field, although the volunteer oats were rarely entirely 
killed — perhaps only changed to a reddish color. The infestation 
seemed to be more marked in the wheat in the vicinity of these spots, 
and later the Toxoptera swarmed about these places. 

It may be noted that these observations of Mr. Ainslie in north- 
western Arkansas, southern Kansas, and northern Oklahoma were 
made upon the same dates as those of the junior author about Fort 
Worth, Tex., and at Hobart in southern Oklahoma, thus covering 
a latitude of nearly 400 miles. 

Mr. Ainslie returned to Kingfisher, Okla., April 3, and was joined 
there by the junior author on the 8th of the same month, where a 
number of experiments were carried out in the field, the results of 
which are given in the proper place. By the 8th of the month para- 
sitized Toxoptera was found excessively abundant in the fields, in 
evidence of which a case was noted where a section of a leaf of wheat 
1J inches in length carried 43 brown, parasitized individuals. Mr. 
Ainslie left Kingfisher, Okla., for Wellington, Kans., on the following 



32 THE SPRING GRAIN-APHIS OR 

day, taking with him more than a bushel of these wheat plants with 
the parasitized Toxoptera thereon and on the 11th this material was 
put out in a field near Wellington where the Toxoptera was the most 
plentiful, in order to determine if it was possible to increase the 
limited numbers of parasites at the time observable in the field, so 
as to expedite the work of the latter in overcoming the pest. This 
was the first artificial introduction of Aphidius into Kansas, six 
days after which Prof. S. J. Hunter began distributing parasites. 
The following day a second lot of material sent from Kingfisher by 
the junior author, some of it carrying as many as 100 parasitized 
Toxoptera to a single blade of wheat, was distributed in a wheat 
field, also near Wellington, by Mr. Ainslie, some of it being placed 
in bunches to protect it from the weather and the remainder scattered 
over the ground among the growing wheat. The Aphidius already 
observed in the fields on the 11th appeared to be on the increase, as 
many as 11 parasitized individuals being observed on a single growing 
leaf, though but few of the adult parasites were observed abroad in 
the fields. On April 18 parasites were sent to McPherson and on 
May 18 to Manhattan, Aphidius being present in the fields at the time 
of introduction. These introductions will be taken up in detail 
farther on in this bulletin. 

On April 12 a letter was received from Mr. J. A. Akers, at Hooker, 
Beaver County, Okla., stating that the "green bug" was destroying 
his wheat. The junior author, being notified of the outbreak, pro- 
ceeded there, arriving on April 24, and found that Mr. Akers' s field 
was the only one in that locality that had been injured, and, in fact, 
it was outside the zone of destructive infestation in this State. This 
field comprised 52 acres, over a portion of which oats had been sown 
the previous year, while cowpeas had been grown upon another and 
much smaller part. Volunteer oats were plentiful over the first 
mentioned area. One of the infested spots was located among the 
wheat and volunteer oats, while the second spot was in the area pre- 
viously devoted to cowpeas. There were no other injured spots in 
the whole field, although an occasional Toxoptera could be found 
here and there over the field, which was also true of other fields in 
this vicinity. It is a significant fact that young plants of Agropyron 
occidentale Scrib. were found growing in both of these spots and they 
were as badly infested as the wheat plants. A few parasitized 
Toxoptera were found, but the parasites were apparently developing 
slowly on account of cold weather. 

The junior author went to Indiana the latter part of the first week 
in May, but was recalled to Kansas and reached Manhattan on thel8th, 
where he was met by the senior author, and a final experiment for the 
artificial introduction of parasites was here planned and begun at 
this time, the results of which are given farther on in the proper place. 



Jul. 1 10, Bureau of Entomology, U. S. Dept. of Agriculture. 



Plate I. 




Fig. 1.— Wheat Field Totally Destroyed by the Spring Grain-Aphis (Toxoptera 

graminum). 

Contrast with uninjured portion of field shown in figure 2. ( Original.) 




Fig. 2.— Circular Spot in Wheat Field where Growing Grain has been Destroyed 
by the Spring Grain-Aphis. 

The growing grain on these circular areas is as completely destroyed as in the field shown in figure 1. 
Increasing in size and number, the spots come to include whole fields. (Original.) 



THE OUTBREAK OF 1907. 33 

From here the junior author made a trip into northwestern and north- 
eastern Kansas and south-central Nebraska to determine the north- 
ern limit of destructive infestation. The following places were 
visited: Solomon, Dickinson County, Kans.; Beloit, Mitchell County, 
Kans. ; Lenora, Norton County, Kans. ; and Kearney, Buffalo County, 
Nebr. The infestation at all of these places was very slight and no 
damage was done. At two places only, Solomon and Beloit, were 
parasites found. 

The senior author in the meantime proceeded to Great Bend, 
Barton County; Dodge City, Ford County; Garden City, Finney 
County; and Syracuse, Hamilton County — all in Kansas. The 
object of this trip was to see how far Toxoptera had spread to the 
westward. It was found at all of the above points, doing consid- 
erable injury; at Syracuse an unirrigated field of oats of 10 acres was 
found bordering an irrigation ditch. Along this ditch was a ragged 
border from 10 to 30 or 40 feet in width of vigorously growing oats 
where the "green bug" had apparently done no injury, while beyond 
this border, where the moisture from the ditch had not penetrated, 
the loss was total. In another case in the same locality, a part of the 
wheat in an unirrigated field came up in the fall and the rest not 
until the following spring; the former was uninjured by "green 
bugs," while the latter was killed. From Syracuse the senior author 
proceeded to Wellington, Kans., to join Mr. Ainslie. 

In a letter dated June 5, 1907, Prof. C. P. Gillette states that he 
made a trip into the Arkansas valley early in the spring and found 
Toxoptera doing very serious injury to wheat fields; to such an 
extent was this the case that he advised some of the farmers to plow 
up some of their fields and plant other crops. Following this trip 
there was a heavy snowstorm and the "green bugs" were greatly 
diminished in numbers, though at the date of his writing (June 5) 
Toxoptera was abundant in the fields. 

On July 9 Prof. Gillette sent us badly parasitized Toxoptera on 
blue grass from Fort Collins, Colo., with the statement that the " green 
bug" had largely disappeared from the grain fields in that locality. 

Mr. Ainslie remained in the vicinity of Wellington, Kans., from the 
last week of April to the 21st of May, at which date he was joined by 
the senior author and went south to Kingfisher, Okla. The condi- 
tions found there were serious in the extreme, most of the grain 
fields being bare and many had been plowed and displaced by other 
crops. Between Wellington, Kans., and Kingfisher, Okla., a strip of 
country was encountered by them about 30 miles in width, beginning 
above Medford, Okla., with Pond Creek about midway between, 
and extending almost to Kremlin, Okla., over which the injury from 
Toxoptera was not nearly so great as in the country both to the 
26675°— Bull. 110—12 3 



34 

north and south. This area was investigated by Mr. Ainslie on the 
23d of May. There was plenty of evidence of Toxoptera attack. 
Some fields were killed outright and others badly spotted, but a 
number of fields were little injured. No particular reason could be 
assigned for this condition of the fields, and this area, with a few 
interruptions, extended on to the west indefinitely. This belt extend- 
ing across the wheat-growing section of Oklahoma was evidently 
observed by Mr. Sanborn, who stated in his notes, copies of which 
were furnished by Prof. Conradi, under date of March 29, 1907, 
"Northern boundary of parasitized infestation is between Kingfisher 
and Enid." Again, under date of March 30, "Pondcreek, Okla. 
Doing great damage, in large spots, here. There lies a peculiar fea- 
ture between this and Kingfisher. At these two points the infestation 
was about equal. Enid has no damage yet." 

Mr. Ainslie now started northward to trace Toxoptera to its most 
northerly point in the United States and to learn to what extent its 
parasite occurred with it, stopping at the following places: Kingman, 
Kingman County, Kans. ; Hutchinson, Reno County, Kans. ; Sterling, 
Rice County, Kans.; Scott, Scott County, Kans.; Great Bend, Barton 
County, Kans.; Oakley, Logan County, Kans.; Colby, Thomas 
County, Kans.; Goodland, Sherman County, Kans.; Manhattan, Riley 
County, Kans.; Lincoln, Lancaster County, Nebr.; Plainview, Pierce 
County, Nebr.; Dixon, Dixon County, Nebr.; Sheldon, O'Brien 
County, Iowa; Mason City, Cerro Gordo County, Iowa; Dodge Center, 
Dodge County, Minn.; Rochester, Olmsted County, Minn.; Brookings, 
Brookings County, S. Dak.; Aberdeen, Brown County, S. Dak.; 
Fargo, Cass County, N. Dak.; East Grand Forks, Polk County, Minn.; 
Hallock, Kitson County, Minn.; Grafton and Park River, Walsh 
County, N. Dak.; Larimore, Grand Forks County, N. Dak.; and 
Casselton, Cass County, N. Dak. He reached the last-mentioned 
place on August 5, after which he returned to Washington, D. C. 

Except at Kingman, Hutchinson, Sterling, Great Bend, and Man- 
hattan, Kans., Mr. Ainslie found but little damage resulting from 
Toxoptera, the most striking feature being the fact that parasites 
were found associated with Toxoptera at each point visited with the 
following exceptions: Goodland, Kans., very few Toxoptera in this 
immediate vicinity; Lincoln, Nebr., no Toxoptera found; Brookings, 
S. Dak., 2 to 3 Toxoptera only seen; Aberdeen, S. Dak., no Toxoptera 
found; Fergus Falls, Minn., only 1 Toxoptera observed here. The 
significant feature of this is that no parasites were introduced artifi- 
cially at any of these points outside of Kansas. 

From statements made by Prof. J. M. Stedman, who was professor 
of entomology at the University of Missouri at this time, it appears 
that Toxoptera was swept over the border from Oklahoma and Kansas 
into southwestern Missouri. Prof. Stedman states that there were 
from six to eight counties in the southwestern corner that were very 



THE OUTBEEAK OF 1907. 35 

badly infested; outside of these counties the infestation was slight. 
He received very few if any reports of its occurrence north of the 
Missouri River. It probably occurred in the northern part of the 
State also, as the bureau received a report, with specimens, of injury 
to oats at Weaver, Lee County, Iowa, and Mr. C. N. Ainslie found 
it occurring in small numbers at several points in northwestern Iowa. 

From reports received by this bureau it seems that Toxoptera was 
very abundant in northern Illinois, confining its injuries chiefly to 
oats. Mr. Edgar McGee, of Sciota, McDonough County, 111., sent us 
specimens July 5 which proved to be Toxoptera, and in a letter dated 
July 29 he stated that it was very widespread, that his and adjoining 
counties were badly infested, and that some fields of oats were so seri- 
ously injured that the owners had plowed them under and planted 
other crops. The yield in that locality, from Mr. McGee's report, 
seems to have been greatly reduced. 

At Sandwich, Dekalb County, 111., there was apparently consider- 
able damage to oats; no specimens were received; the injury in all 
probability was, however, due to Toxoptera. To quote from a letter 
from Mr. Clark Graves, bearing date of July 12 : 

I have today mailed to you, under separate cover, a fair sample of the oats of this 
vicinity, and I think from general appearances that the crop will be shortened half 
on account of the green bug. The bugs have now disappeared, and it would seem that 
the late oats have suffered considerably more than the early ones. 

There were no specimens of plant-lice in this material from Mr. 
Graves. 

A report, with specimens, was received from Manteno, Kankakee 
County, 111., which stated that that section had suffered considerably 
from " green-bug" attack. 

We have only one record of serious injury from Indiana in 1907 
that can without doubt be attributed to Toxoptera. This was in a 
small field of oats just outside the limits of Indianapolis. The junior 
author examined this field and found that over an acre had been seri- 
ously affected, part of it being entirely destroyed. The " green bug" 
disappeared from the oats before the latter headed out, probably 
overcome by Aphidius and other enemies. This infestation appar- 
ently originated from rank bluegrass growing along one side of the 
field. Later in the season, when the oats had been harvested, Tox- 
optera could be found along this margin on the bluegrass, where the 
sexes appeared and eggs were produced. Toxoptera was found at 
other points in Indiana, but only in small numbers. 

Mr. T. H. Parks, of this bureau, states that in the latter part of 
June, 1907, the oats on his father's farm in Pickaway County, Ohio, 
were badly damaged by aphides. He states that parts of some fields 
in the neighborhood were scarcely worth cutting. Aphides were very 
abundant on the plants and parasitized aphides were very plentiful 
also. The oats plants that were badly infested turned brown, and 



36 

before they were ready to head out the aphidids disappeared. This 
was probably due to the presence of the parasites. Wheat was not 
attacked or injured by these aphides. Mr. Parks did not have any 
of this material identified, and we can not say absolutely that this 
was Toxoptera graminum Rond., but the character of the attack, the 
sudden disappearance of the aphidids, and the fact that they did not 
disturb wheat coincide with our observations on this insect in this 
latitude and to us clearly point to Toxoptera as the originator of the 
trouble. 

Part of the trouble referred to in letters cited in Bulletin 210 of the 
Ohio Agricultural Experiment Station was, in all probability, due to 
"green-bug" attack, since from our own observations on this species 
in northern latitudes a part of this injury appears to be characteristic 
of Toxoptera. 

North and South Carolina also suffered somewhat from the depre- 
dations of this insect in 1907. The senior author made a trip into 
this section, reaching Sumter, S. C, April 17, 1907. He found that 
all fields of oats, the only grain sown, were more or less affected; here 
and there brown areas occurred, showing the characteristic work of 
Toxoptera. This condition was noticeable from Sumter, S. C, to 
Charlotte, N. C, indicating that the infestation was general. Both 
Macrosiphum granaria Buckt. and Toxoptera graminum Rond. were 
present, but the latter was by far the more numerous. There were 
very few parasites or coccinellids in evidence. In a letter dated June 
18 Mr. E. C. Haynsworth, of Sumter, stated that soon after the 
senior author's visit in April the weather became warmer and Toxop- 
tera disappeared very rapidly. 

In some parts of North Carolina the injury was quite serious. Mr. 
Franklin Sherman, jr., of the North Carolina Department of Agricul- 
ture, has kindly placed his notes on this outbreak at our disposal. 
He stated that the worst area of infestation centered about Winston- 
Salem, in Forsyth County, N. C, although some injury was also 
inflicted in Guilford, Davie, and Rowan counties in the same State, 
some fields being almost totally destroyed. Parasites were present, 
though not in sufficient numbers to hold Toxoptera in check. 

The senior author went directly from Sumter, S. C, to Winston- 
Salem, N. C, reaching the latter place April 19, where he was met by 
Mr. Sherman, and they went over the ground together. A number 
of fields were examined, ranging from slightly infested to totally 
destroyed. In some fields of wheat, where there had been quantities 
of volunteer oats, the infestation was more severe. Parasites were 
present in great abundance in some fields, but they did not appear to 
have checked the pest in time to save all of the fields. 

The senior author thus summarizes this outbreak: 

From a study of the entire neighborhood it seems quite evident that the outbreak 
of Toxoptera in the vicinity of Winston-Salem was primarily due to the presence of 



Bui. 1 10, Bureau of Entomology. U. S. Dept. of Agriculture. 



Plate II 











&L^W\ 








ppr* g r -.- , -> 




s-*.-.- £Si 4bS..-'3 1' 




k 1 5isSM 


3* -t -lybar -V .. 




^ N *^ , w r 





Fig. 1.— Stand on which Rearing Experiments were Carried Out in Rearing the 
Spring Grain-Aphis. (Original.) 




Fig. 2.— Area on Grounds of the United States Department of Agriculture, 
at Washington, D. C., where the Spring Grain-Aphis Usually Occurs on 
Bluegrass in Excessive Abundance During Summer. 

The area infested is indicated by a +. (Original.) 



THE OUTBREAK OF 1907. 37 

fields of fall oats and more or less volunteer grain in other fields, all of which consti- 
tuted breeding grounds for the pest during the preceding autumn, and from which 
winged individuals migrated and established new colonies in other fields; these, 
owing to influence of weather on the development of parasites, caused the most of the 
injury in wheat. 

We received a letter with specimens from Mr. L. M. Smith, Mr. 
Sherman's assistant, at Newport, Carteret County, N. C, stating that 
he found a small field of oats in the outskirts of town that was con- 
siderably damaged by Toxoptera. This county is on the coast and 
Newport has an elevation of 19 feet. From this it seems that in all 
probability Toxoptera covered the entire State. 

The senior author also found Toxoptera in destructive abundance 
at Midlothian, Chesterfield County, Va., in a small meadow of orchard 
grass. Mr. J. L. Phillips, the State entomologist, reported a slight 
outbreak at Cloverdale, Botetourt County, Va., m rye, and stated 
that considerable damage had been done in some parts of the field. 
One undetermined Aphidius was found at Midlothian, while none was 
reported from Cloverdale. 

There was an outbreak of Toxoptera in the bluegrass lawns north 
of the buildings of the Department of Agriculture at Washington, 
D. C, in July, 1907. The infested area (see PL II, fig. 2) was appar- 
ently confined to the space of about an acre, where it was excessively 
abundant; outside of this area practically no Toxoptera could be 
found. This offered a good opportunity to test spray materials and 
a number of experiments of this kind were carried on. 

Dr. Howard, personally, found Aphidius present in this infested 
area though in very limited numbers. In all probability this was 
Aphidius avenaphis Fitch, as we have since found this species in this 
exact locality but at no time have we found A. testaceipes Cress., 
which, until Mr. Viereck revised this group, had been considered to 
be Lysiphlebus tritici Ashm. We did not, in 1907, find any species of 
Aphidius present and did not know that Dr. Howard had done so, as 
he soon after sailed for Europe and at the time Circular 93 of this 
bureau was published the statement as to its nonoccurrence was not 
called to his attention in time to be corrected and he did not inform 
us of his find, supposing that we knew of it already. Mr. Kelly, how- 
ever, found Allotria sp. present there in 1907, and we have since found 
this to be a parasite of Aphidius, which may account for the fact that 
the latter was present in such limited numbers. In 1908 Aphidius 
avenaphis was quite plentiful there, although specimens were not 
preserved, while Allotria sp. was found sparingly on the grounds else- 
where in the vicinity. As Toxoptera attracted no attention in this 
area on the grounds of the Department of Agriculture in 1909 we 
have no records for that year. In 1910 Toxoptera was again injuri- 
ously abundant on the same area and no Aphidius could be found, 
while Allotria sp.-was still in evidence. It seems possible that condi- 



38 

tions were unfavorable for the rapid increase of Allotria in 1908, 
which conditions would prove favorable for Aphidius and also 
unfavorable for its host, the Toxoptera. This infested area on the 
department grounds in Washington has proved to be of considerable 
interest, as the fluctuations of Toxoptera there, as well as those of its 
parasite Aphidius and the secondary parasite Allotria, must coincide 
with what is going on in similar places over the country, thus forming 
small secluded breeding areas where Toxoptera survives throughout 
the summer, more especially in the South. The area in question is 
a depression covered chiefly by bluegrass, occupying perhaps half an 
acre, surrounded on all sides except*the south by shade trees (See 
PL II, fig. 2.) It is rather more moist and therefore cooler in summer 
than other portions of the grounds and in common with the rest is 
kept closely mown. An underground steam pipe which affords heat 
for a large number of greenhouses extends along the southern and 
eastern margins ; the ground above this pipe is always much warmer 
than the surrounding area during winter, the snow disappearing first 
and the grass in that location starting much earlier in spring. So far 
we have not found that these latter conditions have any influence 
in enabling the Toxoptera to breed viviparously during the winter. 
Even when the Toxoptera was excessively abundant here none could 
be found in the bluegrass-covered grounds only a few yards away, 
except in 1910, when it was quite numerous about the Washington 
Monument some four blocks away. Because of its isolation — there 
are no grain fields within miles on the Maryland side of the Potomac 
River and the department experiment farm at Arlington, Va., has the 
only grain for miles on the west side of the river — and because these 
last had never suffered from Toxoptera attack, this area became of 
too much importance as a convenient field of observation and experi- 
mentation to make an attempt at experimenting with the importation 
of great numbers of Aphidius desirable. There is every reason for 
believing that it is in similar favorable localities that Toxoptera 
passes the summer months in the southwestern portion of the country, 
where, as observations have shown, it is not able to withstand the 
high temperatures of the open fields. 

Toxoptera has been studied throughout the summer in the South- 
west with much difficulty, and not at all satisfactorily for the reason 
that we have been unable to keep it under continuous observation in 
the open fields. 

Except in cases of local outbreaks here and there over the country 
there has been no serious injury to grain crops by the " green bug" 
since 1907. Many additional localities for the species have been 
added since then, however, and it now appears to cover almost the 
entire United States, excepting perhaps New York and the New 
England States. (See fig. 4, p. 19.) 



THE OUTBREAK OF 1907. 



39 



LOSSES FROM DEPREDATIONS IN 1907. 

It is impossible to arrive at the actual monetary loss occasioned 
by this fearful outbreak, as no data have been collected with this 
special end in view, either by the State or National governments. 
Several points must be considered in making such an estimate. 
Large areas planted to wheat and oats were abandoned, part being 
planted to other crops and the remainder left lying idle. Much 
money that was entirely lost was expended in seed, fertilizers, pre- 
paring the seed bed and planting; of course all of the fertilizer 
would not be lost where another crop followed. The greatest source 
of loss came through partial or actual destruction of the young wheat, 
thus greatly reducing the yield. 

The Bureau of Statistics of the Department of Agriculture kindly 
compiled the following table for us, which will shed some light on 
the amount of loss probably attributable to the " green bug." 

Table I. — Losses from depredations by the spring grain-aphis in 1907 in Kansas, 

Oklahoma, and Texas. 

KANSAS. 





Winter wheat. 


Oats. 




Acreage 
planted 
in fall of 
preceding 
year (pre- 
liminary). 


Per 
cent 
aban- 
doned. 


Acreage 
harvested 
(revised). 


Yield 
per 
acre. 


Total pro- 
duction. 


Acreage. 


Yield 
per 

acre. 


Total pro- 
duction. 


1905 


5,645,000 
5,702.000 
5.930,000 
5,930,000 
6,173,000 
6,195.000 


6.3 
10.0 
4.8 
2.5 
4.5 
35.0 


5,290,000 
5,132,000 
5,645,000 
6, 108, 000 
5,895,000 
4,300,000 


Bush. 
13.9 
15.3 
11.3 
12.8 
14.5 
14.2 


Bushete. 
73,527,000 
78,517,000 
63,788,000 
78,182,000 
85,478.000 
61,060,000 


858,000 

1,050,000 

1,092,000 

994,000 

964,000 

1.400,000 


Bush. 
27. 1 
23.6 
15.0 
22.0 
28.2 
33.3 


Bushels. 
23,248,000 
24, 780, 000 


1906 


1907 


16,380,000 


1908 


21,868,000 
27,185,000 
46,620,000 


1909 


1910 














73,425,000 






26,680,000 























OKLAHOMA 










1905: 


















Ind.T 

Okla 

1906: 

Ind.T 

Okla 

1907: 

Ind. T 


286.000 
1,493,000 


5.5 
3.9 


270,000 
1,435,000 


10.0 
8.2 


2,703,000 
11,764,000 


202.000 
294,000 


36.0 
33.0 


7,258.000 
9,717,000 


249.000 
1,403,000 


3.2 
5.0 


241,000 
1,333,000 


12.0 
14.0 


2,890,000 
18,664,000 


218,000 
350, OCO 


34.2 
34.4 


7,447,000 
12,040,000 


216,000 
1,235,000 
1,379,000 
1,241,000 
1,604,000 


28.0 

35.0 

2.3 

6.5 

3.0 














Okla 


959,000 
1,347,000 
1,225,000 
1,556,000 


9.0 
11.6 
12.8 
16.3 


8,631,000 
15,625,000 
15,680,000 
25,363,000 


418, 000 
450, 000 
550,000 
632,000 


15.6 
25.0 
29.0 
36.5 


6, 270. 000 


1908 


11,250.000 


1909 


15,950,000 


1910 


23,068,000 














16,887,000 






15,500,000 

















TEXAS. 



1905 


1,319.000 
1,266.000 
1.266,000 
988,000 
929,000 
1,295,000 


5.3 

3.0 
70.0 

6.5 
27.5 

3.3 


1,249.000 

1.228,000 

380,000 

924,000 

555,000 

1,252,000 


8.9 
11.5 

7.4 
11.0 

9.1 
15.0 


11,118,000 
14,126,000 

2.812,000 
10,164,000 

5.050.000 
18,780,000 


914.000 
914,000 
500,000 
750,000 
615.000 
695,000 


31.4 
34.8 
19.0 
28.9 
18.7 
35.0 


28,713,000 


1906 


31,823.000 


1907 


9, aOO, 000 


1908 


21,675,000 


1909 


11,500,000 


1910 .. 


24,325,000 






Average 










10,342,000 






21,256,000 



















40 

If we average the 5-year period and calculate the loss on this basis 
for 1907, it will be seen that the total crop for Kansas, Oklahoma, 
and Texas fell about 50,000,000 bushels short of this average — both 
wheat and oats being considered. Seventy per cent of the Texas 
wheat acreage was abandoned. 

This does not represent the loss as it actually occurred in various 
parts of the States, as some parts of each State were more badly 
affected than others and the good parts would bring up the yield for 
the poorer portions. Sumner County, Kans., is a good illustration 
of this. It is located in the extreme southern portion of the State 
and was in the badly infested districts. To quote from a letter from 
Mr. George H. Hunter, of Wellington, Kans., dated February 6, 1908: 

I wish to explain that our crop of winter wheat in Sumner County for the year 1907 
amounted to 1,909,574 bushels; this is our latest estimate, while the general average 
is about four and one-half million bushels for Sumner County, and that would be a 
safe basis for you to figure on. According to our acreage last year, if it had not been 
for the green bugs, I think we would have had at least four to four and one-half million 
bushels of wheat. 

THE SITUATION IN 1911. 

The winter and spring of 1910-11 west of the Mississippi River, 
but not east of it, was such as would tend to bring about another 
invasion from the pest. Some injury was reported, accompanied by 
specimens, from Pecos River valley in southeastern New Mexico. 
Mr. J. T. Monell of this bureau, however, visited the locality in 
April and reported the pest as having disappeared without doing 
serious injury. The material received was almost universally para- 
sitized by Apliidius testaceipes Cress., which probably overcame the 
Toxoptera before its occurrence reached the magnitude of an invasion. 

There was also a limited incipient outbreak in eastern Oklahoma, 
which was investigated by Mr. Kelly. Here, too, the parasites 
apparently gained supremacy before serious injury was done, except 
perhaps in a few isolated cases. 

There is little doubt that the unusual and excessively high tempera- 
ture for even a mild winter that prevailed throughout the Southwest 
during a portion of the winter months was sufficient to revive the 
parasites as well as to aid their host, and thus bring about conditions 
that enabled the parasites to prevent the aphidids from increasing in 
numbers to a point where they were beyond their control. 



41 
FOOD PLANTS. 

This insect has a very wide range of host plants and can on that 
account find fresh food at any season of the year. In this way it is 
enabled to perpetuate itself over vast areas of country and under 
almost every variety of climate. 

Rondani, who first described the species in 1852, gives the following 
list of host plants: Oats (Avena sativa); wheat (Triticum vulgare); 
spelt ( Triticum spelta) ; Arrhenatherum elatius (Avena elatior) ; couch 
grass ( Triticum repens) ; Hordeum murinum; Lolium perenne; Capri- 
61a (Cynodon) dactylon; soft chess (Bromus Jiordeaceus) (mollis); and 
corn (Zea mays). He states also that Toxoptera had been found 
quite abundant upon the foliage of rice (Oryza sativa) and common 
barley (Hordeum vulgare). We find no other references to its being 
found upon rice. In 1863 Passerini adds sorghum (Andropogon sp.) 
and he also observed it on barley. 

Macchiati, in 1882, added the following hosts: Dactylis glomerata, 
Bromus erectus, and B. viUosus (maximus); in 1883 he added Triticum 
viUosum, Avena fatua, and A. oarbata; in 1885, Poa annua. 

Del Guercio, in 1906, mentions it as occurring upon buckwheat 
(Fagopyrum esculentum). This is the first and only reference we 
have found in which it has been accused of infesting plants other than 
those belonging to the Graminese. 

Toxoptera was first observed upon wheat and oats in the United 
States. In 1889 the senior author observed it feeding upon rye and 
in 1890 he found it plentiful at Lafayette, Ind., upon Dactylis glomerata. 
In 1907 he found it destructively abundant upon the same grass at 
Midlothian, Va. This infested field was from 4 to 5 miles from wheat, 
oats, or rye fields. In Insect Life, 1 he states that Toxoptera will 
live upon the leaves of all kinds of grains, including corn, during 
summer. In 1902 he found Toxoptera feeding upon cheat (Bromus 
secalinus) and rye grass (Elymus canadensis) at Peotone, 111. 

The junior author found it quite abundant on volunteer corn plants 
among oats on April 2, 1907, at Hobart, Okla. A cornfield near a 
badly infested wheat field was found to be suffering also. Mr. C. N. 
Ainslie of this bureau, on April 4 of the same year, at Kingfisher, 
Okla., found a cornfield that was seriously injured by Toxoptera. 
Farmers in Oklahoma were very much disturbed over the prospect 
that the corn also would be swept away by the " green bug," but later 
developments proved that it was not a serious pest to corn. The 
junior author found Hordeum pusiUum and Alopecurus geniculatus 
badly infested on April 12 at Kingfisher, Okla., and Agropyron occiden- 
tal was found harboring the pest in large numbers at Hooker, Okla., 
in May. The senior author, Mr. Ainslie, and Prof. E. A. Popenoe, 

i Insect life, Div. Ent., U. S. Dept. Agr., vol. 4, p. 245. 



42 

of Kansas, also found the Hordeum pusillum much infested later in 
the season. In July there was an outbreak of Toxoptera on blue- 
grass (Poa pratensis) on the grounds of the United States Department 
of Agriculture, Washington, D. C. Later in the season the junior 
author found it on bluegrass in the fields about Richmond, Ind. 
In the fall of the same year (1907) this was the only plant on which 
the sexes and eggs could be found. In fact, for Indiana, Illinois, 
Ohio, and more northern localities bluegrass appears to be the normal 
host, and the " green bug" is readily found upon it at any time in 
the year even when it can be found only sparingly upon any other 
plant. 

A number of new host plants were added to the fist in 1908. Mr. 
Kelly, of this Bureau, found Toxoptera feeding freely in the fields 
upon Hordeum jubatum and Distichlis spicata in Montana and upon a 
species of Andropogon in Colorado. Mr. Ainslie found it breeding 
freely in the fields upon Hordeum jubatum, H. cxspitosum, H. nodosum, 
Mymus striatus, Agropyron tenerum, Bromus unioloides, B. porteri, 
Stipa viridula, and Polypogon monspeliensis about Artesia, N. Mex. 
In one instance Mr. Ainslie found several alfalfa plants {Medicago 
sativa) with colonies of Toxoptera upon them, as many as 21 speci- 
mens being observed on a single leaf. This seems very unusual and 
we have no other records of its occurrence on this plant. Prof. C. P. 
Gillette, of Fort Collins, Colo., found it infesting Agropyron occidentdle, 
and in 1907 he found it feeding upon bluegrass. During the summer 
of 1908 Toxoptera was found by the junior author to breed freely 
upon Dactylis glomerata, Eleusine indica, Eragrostis pilosa, E. megas- 
tachya, Sporobolus neglectus, Agropyron repens, Elymus virginicus, 
E. canadensis, and Bromus secalinus, in his rearing cages at Rich- 
mond, Ind. 

In 1909 and 1910 a few more plants were added to the list. Mr. 
Ainslie found it breeding freely upon Hordeum murinum in Arizona and 
upon Agropyron occidentdle in New Mexico. Mr. Kelly found it 
breeding freely upon millet (CJisetocloa italica) and upon Japanese 
millet (Echinochloa crus-galli) in Kansas. Mr. Harper Dean, jr., then 
of this bureau, found it feeding upon Stipa leucotricha in Texas. Mr. 
T. D. Urbahns, of this bureau, found that it bred readily in his cages 
at Dallas, Tex., upon Bermuda grass (Capriola dactylon), Chsetochloa 
viridis, Johnson grass {Sorghum Jialepense), and upon rice (Oryza 
sativa). 

During the summer of 1909 Mr. T. H. Parks, of this bureau, and 
the junior author observed that Toxoptera bred freely upon Mymus 
striatus, Juncus tenuis, Poa compressa, Bromus commutatus, B. tec- 
torum (?), B. inermis, sheep's fescue (Festuca ovina), hard fescue 
(F. duriuscula), meadow fescue (F. elatior), various-leaved fescue 



FOOD PLANTS. 



43 



(F. TieteropTiyUa) , F. rubra, Agropyron occidentale, and Italian rye 
grass (Lolium multiflorum), in their rearing cages at Lafayette, Ind. 
The following is a complete tabulated list of host plants 1 to date, 
in so far as our records show. 



IN EUROPE. 



Barley. 

Corn. 

Oats. 

Rice. 

Wheat. 

Spelt. 

Sorghum. 

Agropyron (Triticum) repens. 

Avena barbata. 

Avena elatior= Arrhenatherum elatius. 

Avena fatua. 



Bromus erectus. 
Bromus maximus=B. villosus. 
Bromus mollis=B. hordeaceus. 
Capriola (Cynodon) dactylon. 
Dactylis glomerata. 
Fagopyrum esculentum. 
Hordeum murinum. 
Lolium perenne. 
Boa annua. 
Triticum villosum. 



IN AMERICA, 



Barley. 

Corn. 

Oats. 

Rice. 

Rye. 

Sorghum. 

Spelt. 

Wheat. 

Alfalfa (Medicago sativa). 

Agropyron occidentale. 2 

Agropyron repens. 

Agropyron tenerum. 2 

Alopecurus geniculatus. 2 

Cheat (Bromus secalinus). 2 

Bromus commutatus. 2 

Bromus inermis. 2 

Bromus porteri. 2 

Bromus tectorum (?). 2 

Bromus unioloides. 2 

Capriola dactylon. 

Chsetochloa italica. 

Chsetochloa viridis. 2 

Dactylis glomerata. 

Distichlis spicata. 2 

Echinochloa crus-galli. 2 



Eleusine indica. 2 
Elymus canadensis 2 
Elymus striatus. 2 
Elymus virgin icus. 2 
Eragrostis megastachya. 2 
Eragrostis pilosa. 2 
Festuca duriuscula. 2 
Festuca heterophylla. 2 
Festuca ovina. 2 
Festuca elatior. 
Festuca rubra. 2 
Holcus halpensis. 2 
Hordeum csespitosum. 2 
Hordeum jubatum. 2 
Hordeum murinum. 
Hordeum nodosum. 2 
Hordeum pusillum. 2 
J uncus tunuis. 2 
Lolium, multiflorum. 2 
Poa compressa. 2 
Poa pratensis. 2 
Polypogon monspeliensis. 2 
Sporobolus neglectus. 2 
Stipa leucotricha. 2 
Stipa viridula 2 



i During 1909 Mr. C. P. v. d. Merwl, Bloomfontein, Orange Free State, Africa, wrote us that lie had 
found Toxoptera graminum attacking "Bermuda grass " and their native blue-grass (Andropogon hirtus). 
2 These are host plants not previously recorded. 



44 

CHARACTER OF ATTACK. 

The actual effect upon the plant, whether chemical or physiological, 
is not clearly understood. If a f ew Toxoptera be placed upon a per- 
fectly healthy plant, in a few days the tissue in the immediate 
vicinity of the aphidids will take on a yellowish tinge; if the aphidids 
remain in one place for a considerable time and increase in numbers, 
the whole plant gradually turns yellow and dies, the leaves changing 
to reddish brown. 

When the original source of infestation arises from some one or 
more points within a field, as described elsewhere in this paper, the 
plants take on a yellowish color in small, almost circular areas, (PI. 
I, fi.g. 2) and as the Toxoptera increase in numbers the plants in the 
center die, becoming reddish brown, and the aphidids work outward 
in every direction from the center, gradually enlarging the spot until 
it may cover many acres. When a field is infested from without by 
migrating forms, the aphidids appear to spread evenly over the entire 
field and the whole gradually turns yellow, and in cases of severe 
outbreaks a whole field may die simultaneously. (See PL I, fig. 1.) 
These aphidids are essentially leaf-feeders, rarely if ever being found 
injuring the heads or fruiting parts of the plant. 

Toxoptera appears to have a more strikingly disastrous effect upon 
wheat or oats plants than any of the other common grain aphidids. 
Seemingly when in no greater numbers than other species the plants 
will succumb more quickly to the attack of Toxoptera. 

VIVIPAROUS DEVELOPMENT. 

Toxoptera graminum, as already shown, has been found to breed 
over a wide range of country, and its behavior, under the varying 
temperatures and climatic conditions prevailing over this vast terri- 
tory, presents and opens up a broad field for investigation. 

IN THE SOUTH. 

In northern latitudes the normal manner of reproduction among 
the Aphididse is both sexually and asexually. In southern latitudes 
hese conditions, apparently, do not obtain, as here the normal means 
of reproduction seems to be asexually, each generation being com- 
posed entirely of viviparous females. 

South of about the thirty-fifth parallel, except in high altitudes, it 
appears that Toxoptera breeds continuously throughout the year 
without the appearance of the true sexes. April 6, 1906, Mr. George I. 
Reeves, of this bureau, found the eggs of a plant-louse on wheat at 
Nashville, Tenn., and Mr. Kelly found males (fig. 6), females, and 
eggs of Toxoptera at Knoxville, Tenn., in December, 1908. The 
eggs found by Mr. Reeves may have been those of Toxoptera, but we 



VIVIPAROUS DEVELOPMENT IN SOUTH. 



45 




re 



I 

8 



46 



THE SPUING GRAIN-APHIS OR " GREEN BUG. ' ' 




VIVIPAROUS DEVELOPMENT IN SOUTH. 



47 



can not be sure of the species as they were not reared. Winged and 
wingless viviparous females (figs. 7, 8) were, however, present at the 
time the eggs were found, as were also those of both Aphis (Sipho- 
coryne 1 ) and Macrosiphum. Mr. E. Dwight Sanderson obtained the 
males and oviparous females of Macrosiplium granaria Buckt. in 
Texas but only artificially in his rearing cages. Mr. R. A. Vickery, 
of this bureau, found males, females, and eggs of Aphis maidi-radicis 
Forbes at Salisbury, N. C. These instances mentioned above are 
probably the most southerly points at which oviparous forms of 
plant-lice have so 
far been found in 
the United States. 

In the Southern 
States, wherever 
there is sufficient 
food, Toxoptera 
apparently breeds 
viviparously 
throughout the 
year; for this rea- 
son the number of 
generations here, 
other things being 
equal, should far 
exceed that in the 
Northern States. 
As a matter of fact, 
however, the dry, 
hot, protracted 
summers of the 
Southwest are 
probably disas- 
trous to the species during the hot months, except perhaps in 
secluded nooks, where there is a supply of succulent host plants. 

In northern Texas, as observed by Mr. Urbahns, during June of 
1909, Toxoptera rapidly disappeared with the ripening of the grain 
crops and the approach of hot weather. Winged forms migrated 
with the breeze early in this month, and wingless forms soon perished 
from extreme heat and a shortage of green food in the field. Obser- 
vations clearly showed that it was almost impossible for the " green 
bug" to live and reproduce in grain fields during the summer. While 

1 Probably Siphocoryne avenx Fab. The use of the generic name Siphocoryne, as applied to this species, 
is questionable, and is not at present followed by many, perhaps the major portion, of the students of the 
Aphididae. According to Schouteden (Ent. Soc. Belgique, vol. 12, p. 217, 1906, Catalogue Aphides de 
Belgique) it should be Aphis. Some of our best students, however, admit that this particular species, 
avenx, is on the borderland between Siphocoryne and Aphis. 




Fig. 8. — The spring grain-aphis: Wingless viviparous female. Enlarged; 
actual size, 2 mm. (Original.) 



48 THE SPRING GRAIN-APHIS OR " GREEN BUG. ,, 

the temperature was above and precipitation below normal, during 
this particular season, the effect was so evident that there is reason 
to believe that under normal conditions these aphidids do not live in 
fields directly exposed to the sun during the summer months. 

The table on pages 64-69 on daily reproduction, length of 
reproductive period, and longevity show a decided decrease in all of 
these for the summer months over those of spring and fall. The facts 
upon which these figures were based could be secured only by pro- 
tecting the aphidids from exposure to the hot summer sun. Aphidids 
exposed without such protection were unable to live through the 
season, though special care was taken to furnish them with a supply 
of green food plants. 1 

Mr. Urbahns secured the following results by removing Toxoptera, 
together with its green food plants, from a shaded position and sub- 
jecting it to the temperature of loose, unshaded soil. 

August 18, with the soil temperature at 145° F. in the sun, 12 Toxoptera on a wheat 
plant were exposed 30 seconds; 5 fell to the ground dead, 7 remained on the plant 
dead. 

Three adults and 4 young on a wheat plant were similarly exposed for 30 seconds, 
after which time all were dead. 

One winged and 4 wingless adults on a wheat leaf were exposed for 30 seconds, 
when they were found to be dead on the plant. 

Thirteen adult aphidids on wheat plants were exposed for 15 seconds, 5 fell to the 
ground dead. After 30 seconds exposure the plant was removed to the shade; 6 more 
were then dead on the plant and 2 were alive between the leaves. 

Soil temperature 118° F. (shaded by cloud). Nine aphidids on a wheat plant were 
exposed for 30 seconds, 2 died, and 7 remained alive. 

A ported wheat plant bearing several hundred aphidids, the temperature being 114° 
F. in the shade, was removed from the shade for 5 minutes. A large percentage of 
the aphidids fell to the ground, some survived, but many died. 

A potted wheat plant bearing several hundred aphidids was kept in the shade where 
the maximum temperature was 114° F. Next morning many of the aphidids were 
dead. 

When the soil temperature was 116° F. shaded by a thin cloud, 3 aphidids on a plant 
were exposed for 60 seconds, 1 died, and 2 remained alive. 

August 19, the soil temperature being 128° F. in the sun, 12 aphidids on a young 
plant were exposed for 30 seconds; 5 fell from the plant and died, while the other 7 
were dead on the plant. 

When the soil temperature was 130° F. in the sun 12 aphidids on a young plant were 
exposed for 20 seconds. All were then dead. 

When the soil temperature was 128° F. in the sun 11 aphidids on a plant were exposed 
for 30 seconds; at the end of this time all were dead — 4 fell to the ground, and 7 
remained on plant. 

At a soil temperature of 130° F. in the sun 8 aphidids on a plant were exposed for 15 
seconds; all were then dead — 3 fell to the ground, and 5 remained on the plant. 

The results of these experiments prove that Toxoptera can not 
survive the summer in the open fields in sections of the country 
where the pest commits its most serious ravages with the greatest 

i Mr. J. T. Monell suggests that this may be due as much or more to the hot, dry air as to the direct 
rays of the sun. 



VIVIPAROUS DEVELOPMENT IN NORTH. 49 

frequency. They also account for our inability to locate it in such 
territory during the summer months. 

A careful search was made at different times for grasses that 
were actually serving as summer food plants. The only hope of 
finding such was in well shaded spots along streams, where, from all 
indications, Toxoptera would be sufficiently protected to live and 
reproduce throughout the summer. 

At Piano, Tex., Toxoptera was rapidly disappearing from the 
fields in early June. By June 14 there was only a limited number 
of plants which still supported the remaining few of these aphidids 
and the latter were soon carried away by ants. When confined on 
green food plants and protected from their enemies by a large frame 
covered with thin cheesecloth Toxoptera lived until July 3. After 
this date it was apparently too hot for their existence. Out in the 
open, where young wheat and oats plants were sustained by frequent 
watering, they lived until July 15. After this date they apparently 
could not endure the summer temperature and no more were found. 
Since no reinfestation appeared up to November 30, it was quite 
evident that the aphidids had all perished. 

On June 28 viviparous forms of this species were found rather 
abundantly in a small field of oats at McAlester, Okla. This field 
of a few acres in size was on the east slope of a rocky hill. A natural 
growth of timber surrounded the field and a few trees grew in its 
midst where rocks make cultivation impossible. Green vegetation 
was abundant in shaded places and along the creek one-half mile to 
the east. Conditions of this sort are certainly favorable for Toxoptera 
to five and reproduce throughout the summer as long as they find the 
food plants present. While these spots, favorable to Toxoptera, are 
characteristic of eastern Oklahoma, where, as has been stated, an 
incipient outbreak of the pest actually occurred in 1911, they are 
also found along streams in the central part of that State and in 
northern Texas. As there appears to be no resting or egg stage in 
the South, whenever there is a warm open winter these' aphidids 
become very abundant and threaten the grain crops of this region. 

IN THE NORTH. 

Farther north, in the vicinity of Lafayette, Ind., viviparous repro- 
duction is confined to the months of April, May, June, July, August, 
September, October, and November. During mild winters, how- 
ever, the species may breed viviparously throughout the year, as the 
senior author found it breeding in the open throughout January, Feb- 
ruary, and March, 1890, notwithstanding the fact that on January 24 
the temperature fell as low as + 3° F.; on February 9, to + 6° F., 
and on March 6 to + 4° F. It appears that a temperature of about 
26675°— Bull. 110—12 i 



50 



THE SPRING GRAIN-APHIS OR 



zero, with no protection, is fatal to Toxoptera, except to the egg, but 
the fact that it withstood the winter in 1890 can easily be accounted 
for. That winter was unusually mild throughout, with the excep- 
tion of the dates mentioned, and if one consults the weather records it 



Fig. 9.— The spring grain-! 




s: Oviparous female, showing eggs within the abdomen, 
actual size, 2.25 mm. (Original.) 



Enlarged; 



will be found that on January 24 there were 3.5 inches of snow, Feb- 
ruary 9, 3.4 inches, and March 6, 4 inches. The covering of snow in 
each instance would appear to have been sufficient to protect the 
Toxoptera, as on December 8, 9, and 10, 1909, at Lafayette, Ind., 
the temperature fell as low as from — 1° F. to —4° F. below zero, and 

plant-lice of all kinds, in 
the rearing cages out of 
doors, were killed, while 
those in a near-by wheat 
field, covered with several 
inches of snow, were found 
to be in good condition on December 13, at which time the cold 
spell was broken and the ground began to thaw. 

As a rule, Toxoptera breeds slowly in October and November, at 
which time the majority become oviparous females (figs. 9, 10) and 
males (fig. 6). 




Fig. 10.— The spring grain-aphis: Hind tibia of oviparous 
female. Greatly enlarged. (Original.) 



THE SPRING GRAIN-APHIS OR ' ' GREEN BUG. ' ' 



51 



REARING METHODS. 



All of the rearing work, unless otherwise stated in the text, was 
conducted out of doors under as nearly normal conditions as it was 
possible for us to secure. The wheat plants on which the Toxop- 
tera were confined were grown in flowerpots and covered with 
lantern globes, over the top of which was drawn a very thin fabric 
commercially known as swiss. The 
pots were placed on a rearing stand 
having one side hinged in such a 
manner that it could be let down in 
fair weather and closed up in case of 
gales or severe beating storms. This 
stand with its contents is illustrated 
in Plate II, figure 1 . A thermograph 
was placed in this stand, and thus 
continuous records of temperature 
were secured. 

In the middle of the summer of 
1907 two series of investigations were 
begun and were continued until De- 
cember to determine the number of 
generations. In both 1908 and 1909 
series of generation studies were begun 
in spring with the egg (fig. 11) and 
continued until the egg-laying forms 
appeared in the fall. In making these 
observations, the first individuals to 
hatch from the eggs in the spring 
were isolated; the first-born from 
these were in turn isolated, and this 
process was continued throughout the 
season until the egg-laying forms ap- 
peared. The last-born was also kept 
and the same mode of procedure con- 
tinued until fall, as was the case in the line of the first-born. All 
young other than the first-born of the first series and the last-born 
of the second series were counted each day and destroyed. In this 
manner, each series being considered, we would arrive at the maxi- 
mum and minimum number of generations. During these three years 
a vast amount of data, besides that on the number of generations, 
was thus accumulated. (See table, pp. 52-57.) 




Fig 



11.— The spring grain-aphis: Eggs as 
deposited on leaf: a, Dorsal view; 6, lat- 
eral view. Greatly enlarged. (Original.) 



52 



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REARING METHODS. 



57 



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58 

STEM MOTHERS. 

At both Richmond and La Fayette, Ind., the eggs begin to hatch 
the latter part of March and continue until about April 10. The 
first generation, or stem mothers, differs from the next generation 
slightly in coloration, and there are besides some slight structural 
differences. The measurements of the body are not included in the 
following description, as the specimens are mounted in balsam. 

DESCRIPTION OF THE DIFFERENT IN STARS. 

First instar. — Before first molt: General color, very dark Nile green; head, beak, 
antennae, legs, and cornicles very dark gray; tips of the antennae, the tarsi, and the 
eyes black. Antennae 4-segmented. 

Measurements of antennal joints (average from 2 specimens): I, 0.034 mm.; II, 
0.034 mm. ; III, 0.093 mm. ; IV, base, 0.046 mm. ; IV, filament, 0.114 mm. ; total length, 
0.321 mm. 

Second instar. — Before second molt: General coloration of head and body lighter 
than in the preceding stage, otherwise the coloration the same. Antennae 5-segmented. 

Measurements of antennal joints (average from 3 specimens): I, 0.045 mm.; II, 
0.039 mm.; Ill, 0.127 mm.; IV, 0.082 mm.; V, base, 0.066 mm.; V, filament, 0.161 
mm.; total length, 0.520 mm'. 

Third instar. — Before third molt: The color of the body now varies from pale green 
to deep apple green; head concolorous with body; legs slightly lighter; eyes, tip of beak, 
tip of cornicles, articulation of femora, and tibiae black; distal two-thirds of antennae 
black; basal portion greenish gray. Antennae 5-jointed. 

Measurements of antennal joints (average from 4 specimens): I, 0.050 mm.; II, 
0.045 mm.; Ill, 0.152 mm.; IV, 0.093 mm.; V, base, 0.072 mm.; V, filament, 0.174 
mm.; total length, 0.586 mm. 

Fourth instar. — Before fourth molt; General coloration variable, though about the 
same as in third instar, with the exception that the eyes of the young begin to show 
through the body wall; eyes and tip of beak black; legs greenish gray, the articulation 
of femora and tibiae and the distal portion of tibiae very dark, and tarsi black; cauda 
lighter than the body, as is sometimes also the head ; the two distal segments and distal 
portion of third segment of antennae black, gradually shading off until at the base they 
are concolorous with the head; cornicles black at tips, shading off into pale grayish 
green at base. Antennae 5-jointed; sometimes, however, there are 6 distinct joints. 

Measurements of antennal joints (average from 4 specimens): I, 0.065 mm.; II, 
0.051 mm.; Ill, 0.194 mm.; IV, 0.119 mm.; V, base, 0.088 mm.; V, filament, 0.196 
mm.; total length, 0.713 mm. 

Fifth instar. — In the adult stage the color varies from a clay yellow to greenish yellow 
and deep apple green; there is no central dorsal stripe; the eyes of the young show 
through the body walls. In some of the greener specimens the head is slightly lighter 
and in some of the lighter colored specimens the head is slightly darker than the body; 
eyes and tip of beak black; legs pale greenish gray, the articulation of femora and 
tibiae and the distal third of tibiae quite dark; tarsi black; cauda in yellow specimens 
with a yellowish tint and in the deep green specimens somewhat grayish, shape and 
length same as in summer form; cornicles concolorous with body except the distal 
third, which is black, shape and length same as in summer form; three distal segments 
of antennae and distal half of fourth black, the basal joints concolorous with the head. 
Antennae 6-segmented, though two specimens were found in which one antenna of each 
was only 5-segmented. 



DESCRIPTION OF SUMMER FORMS. 



59 




Fig. 12. — The spring grain-aphis: 
Young, first instar. Enlarged; 
actual size, 0.75 mm. (Original.) 



Measurements of antennal joints (average from 16 specimens): I, 0.066 mm.; II, 
0.049 mm.; Ill, 0.226 mm.; IV, 0.140 mm.; V, 0.152 mm.; VI, base, 0.091 mm.; VI, 
filament, 0.225 mm. ; total length, 0.951 mm. They are slightly pruinose in each stage. 

The material from which these data were taken is mounted on slides and is in the 
collections of the Bureau of Entomology, bearing Webster number 5151. 

The first generation, or stem mothers, is always wingless. All of the following gener- 
ations differ in color, more especially in the first and second instars. The adult stem 
mothers, so far as we have been able to learn, never 
have the darker green dorsal stripe. The antennae 
are shorter throughout the different instars, and in 
the adult also, than in the summer forms. 

DESCRIPTION OF THE SUMMER FORMS. 

First instar {fig. 12). — Before first molt: General 
color very pale green, the thorax probably the palest; 
head pale green with a dusky tinge; eyes brownish 
black; tip of cornicles black, bases dusky; articula- 
tion of femora and tibiae and distal portion of tibiae 
dusky; tarsi black; two apical segments of antennae 
black, remaining segments concolorous with head. 
Antennae 4-segmented. 

Measurements of antennal joints (average from 3 specimens): I, 0.032 mm.; II, 
0.033 mm. ; III, 0.118 mm. ; IV, base, 0.049 mm. ; IV, filament, 0.154 mm. ; total length, 
0.386 mm. 

Second instar (fig. 13). — Before second molt: General color slightly paler now; head 
not dusky; eyes same as in preceding stage; legs with a more greenish tinge now, other- 
wise same as in previous stage; the two basal joints and the proximal portion of the 
third joint of antennae concolorous with head, other portion black. Antennae 5-jointed. 

Measurements of antennal joints (average from 2 
specimens): I, 0.041 mm.; II, 0.035 mm.; Ill, 0.106 
mm.; IV, 0.075 mm.; V, base, 0.062 mm.; V, fila- 
ment, 0.204 mm.; total length, 0.523 mm. 

Third instar. — Before third molt: Coloration prac- 
tically same as in second instar; eyes almost black; 
bases of cornicles paler than abdomen. Antennae 
5-jointed. 

Measurements of antennal joints (average from 2 
specimens): I, 0.056 mm.; II, 0.045 mm.; Ill, 0.172 
mm.; IV, 0.099 mm.; V, base, 0.076 mm.; V, fila- 
ment, 0.259 mm.; total length, 0.707 mm. 

Fourth instar. — Before fourth molt: General color 
deeper green now, very close to apple green; dorsal 
stripe apparent in this stage at times, eyes of young 
showing through body wall at this time, head a shade 
lighter than body and sometimes seeming to be tinged 
with yellow; eyes brownish black; beak black at tip; legs more of a yellowish green 
now, the articulation of femora and tibiae and the distal portion of the tibiae dusky; 
tarsi black; the two apical segments of antennae black, next much lighter, third 
slightly dusky, and the two basal segments concolorous with head. Antennae 5-seg- 
mented, although sometimes they appear to have 6 segments. 

Measurements of antennal joints (average from 2 specimens): I, 0.060 mm.; II, 
0.045 mm. ; III, 0.272 mm. IV, 0.120 mm. ; V, base, 0.086 mm. ; V, filament, 0.282 mm. ; 
total length, 0.865 mm. 
All of the above stages slightly pruinose. 




Fie. 13. — The spring grain-aphis: 
Young, second instar. Enlarged; 
actual size, 0.922 mm. (Original.) 



60 THE SPRING GRAIN-APHIS OR 

The following is the description of the adult, summer forms, as 
given by Mr. Pergande: x 

Apterous female [fig. 8]. — Length 1-1.8 mm.: color yellowish green and slightly prui- 
nose, the median line darker green, the head and prothorax somewhat paler than the 
rest of the body. Eyes black. Antennae black, the two basal joints and more or less 
of the third joint at base yellowish. Legs yellowish, the tibiae brownish toward the 
apex, tarsi black. Tail dusky. The general color of the larvae and pupae is like that 
of the apterous female. Wing pads of pupa dusky to black. Antennae slender and 
about one-half the length of the body. Nectaries slightly tapering, reaching to or 
slightly beyond the end of the body. Tail slender, somewhat constricted about the 
middle, and about two-thirds the length of the nectaries. There is a distinct fleshy 
tubercle each side of the prothorax and similar tubercles along both sides of the abdo- 
men. 

Migratory female [fig. 7]. — Ex- 
panse of wings 5-7 mm. ; length 
of body 1.5-2 mm. General 
coloration of the abdomen as 
in the apterous forms; head 
brownish yellow; the eyes 
brown; antennae, thoracic 
lobes, the posterior margin of 
the scutellum, and the sternal 
plate black; the two basal 
joints of the antennae yellowish 
green; legs yellow, the femora 
more or less dusky, the posterior 
pair darkest; apex of tibiae and 
the tarsi black; nectaries and 
tail yellowish, the latter chang- 
ing gradually to dusky or 
black toward the end; wings 
transparent; costa and subcosta 
yellow; the stigma somewhat 
paler, its inner edge and the 
veins black. Third discoidal 

vein with but one fork. An- 
FIG. 14.-The spring grain-aphis: Pupa of winged viviparous ^^ ^ glend reach _ 
female. Enlarged; actual size, 1.875 mm. (Original.) ° ' 

mg nearly to the end of the 

body, the third joint provided with 3 to 7 sensoria. Nectaries, tail, and lateral 

tubercles, as in the apterous females. 

Besides the sensoria on the third segment of the antennae mentioned 
in the above description, there are from 1 to 2 on the fourth, 1 near 
the apex of fifth, and several, more or less distinct, on the base of tne 
sixth. 

Measurements of antennal joints (average from 8 specimens): I, 0.082 mm.; II, 
0.059 mm.; Ill, 0.300 mm.; IV, 0.223 mm.; V, 0.215 mm.; VI, base, 0.110 mm.; 
VI, filament, 0.395 mm.; total length, 1.384 mm. 

To this description we add : 

Wingless female (fig. 8).— Coloration for this stage varying from a very pale green 
with a slight tinge of yellow to a deep apple-green. The dorsal stripe is not always 

i Bulletin 38, Div. Ent., U. S. Dept. Agr., p. 18, 1902. 




MOLTING. 61 

present. The size varies greatly in nearly all forms, wingless viviparous females 
varying from 1.5 mm. to over 2 mm. 

Measurements of antennal joints (average for 8 specimens): 1, 0.069 mm.; II, 
0.045 mm.; Ill, 0.210 mm.; IV, 0.135 mm.; V., 0.140 mm.; VI, base, 0.089 mm. 
VI, filament, 0.305 mm.; total length, 0.993 mm. 

Pupae (fig. 14). — Measurements of antennal joints (average from 8 specimens): 
I, 0.064 mm.; II, 0.056 mm.; Ill, 0.186 mm.; IV, 0.127 mm.; V, 0.134 mm.; VI, 
base, 0.090 mm.; VI, filament, 0.270 mm.; total length, 0.927 mm. 

Winged viviparous female (fig. 7). — Measurements of antennal joints (average from 
8 specimens): I, 0.082 mm.; II, 0.059 mm.; Ill, 0.300 mm.; IV, 0.223 mm.; V, 
0.215 mm.; VI, base, 0.110 mm.; VI, filament, 0.395 mm.; total length, 1.384 mm. 

MOLTING. 

The time required for molting, from beginning to completion, is 
30 minutes. The first indication is restlessness; the antennae are 
waved continuously and the legs move jerkily. This period of 
restlessness continues for 10 minutes, after which the antenna? are 
allowed to come to rest close down upon the dorsum. A few minutes 
later the tip of the abdomen will appear transparent and baggy, due 
to the old skin having slipped backward ; the head and eyes are now 
being freed. It appears that the skin 'first ruptures in the cephalic 
region and only splits a part of the length of the dorsum, the insect 
gradually working its way out from this extremity. After the head, 
the antennas are the first to be liberated, then each pair of legs in 
succession, and after all of the appendages have been freed the insect 
has still to struggle somewhat to free its abdomen. These observa- 
tions were made on individuals casting the third or fourth molt. 

NUMBER OF MOLTS. 

Quite a number of observations were made on the number of molts 
and the period between the same, it being learned that stem mothers, 
the summer forms, and the sexes molt 4 times only. 

To facilitate careful and accurate observations upon the number of 
molts, a young wheat plant was potted in a 5-inch flowerpot. A 
circle of black paper was cut small enough to fit down in the top of 
the pot. A small hole was then cut in the center and the paper disk 
was then fitted closely down about the base of the plant. After the 
paper was in place the space immediately around the plant was filled 
in with absorbent cotton made black with waterproof ink. Then a 
young Toxoptera that had just been born was placed on the plant 
inclosed by a clean lantern globe, with a piece of new cheesecloth 
firmly secured over the top to prevent the grayish cast skins from 
being overlooked. Each cast skin was removed as soon as the molt 
was completed, and a record made so that it could not possibly be 
counted a second time. All observations recorded in the notes on 
molting were made in this manner. 



62 

During the summer of 1907, at Richmond, Ind., careful observa- 
tions were made on 7 individuals of the summer forms, and in the fall 
Mr. R. A. Vickery, of this bureau, made observations on 6 indi- 
viduals, 3 of which proved to be males and 3 oviparous females. 
In each case there were 4 molts. In the spring of 1908, 4 stem moth- 
ers were found to molt 4 times only. In the spring of 1909 at Lafay- 
ette, Ind., 1 stem mother was found to molt 4 times. Later on in the 
summer, Mr. T. H. Parks, of this bureau, ran a series of experiments 
with the summer forms and, of the 30 individuals under observation, 
some of which were winged, he found that all without exception 
molted 4 times. In the fall of 1910 several additional oviparous 
females were found to molt 4 times only. This makes a total of over 
50 specimens that came under our observation, under conditions that 
would absolutely preclude error, and there was not a single excep- 
tion — all molting 4 times. 

As it was found that the period between molts varied, experiments 
were begun in the summer of 1907 at Richmond, Ind., in order to 
learn how great the variation was when each individual was subjected 
to the same conditions. 1 This experiment was carried on indoors 
and all individuals were subjected to the same conditions. Table II 
will show the variations. 



Table II. — Variation in the duration of the different instars in Toxoptera graminum. 



Individual. 


From time 
of birth to 
first molt. 


From first 
molt to sec- 
ond molt. 


From sec- 
ond molt to 
third molt. 


From third 

molt to 
fourth molt. 


A 


H. m. 
38 35 
40 15 
50 20 
45 
44 30 


H. m. 

28 29 

29 15 
26 40 
54 

32 35 


H. m. 
31 37 

34 36 

35 48 
40 

36 50 


H. m. 
39 40 


B 


34 37 


c 


40 22 


D 

E 


64 
39 37 







There is also considerable variation in the time from birth of 
individuals to the fourth molt and the appearance of the first young, 
as will be seen from Table III. Individuals in Table III are the 
same as in Table II, with the addition of "F" and "1& 3 ." 

Table III. — Variation in the time from birth of individuals to fourth molt and appearance 
of first young in Toxoptera graminum. 



Individual. 


From time of birth to 
fourth molt. 


From time of birth until 
first young appear. 


A . 


Hours. 

143-144 
143 
153 
153 
204 
195 

170-175 


Days. 
5.9 
5.9 
6.3 
6.3 
8.5 
8.1 
7.1 


//. m. 

144 35 

148 

164 

165 

246 

205 
2 175 


Days. 
6.02 


B . 


6.1 


c . 


6.8 


D . 


6.8 


E 


10.02 


F 


8.5 


16 3 


7.2 







Proc. Ent. Soc. Wash., vol. 10, Nos. 1-2, pp. 11-13, 1908. 



* Approximate. 



NUMBER OF GENERATIONS PER YEAR, 63 

BIRTH OF YOUNG. 

In the fall of the year 1907 adult individuals of Toxoptera were 
brought from out of doors into a warm room ; placed under a micro- 
scope, and observations made on the manner of birth of the young. 
The embryonic young within the body of the parent are inclosed 
within a thin, transparent, structureless membrane that corresponds 
to the vitelline membrane in the true egg. Normally, in warm 
temperatures, the young Toxoptera frees itself from this enveloping 
sac during birth. At a temperature of about 60° F. or below, the 
young are oftentimes dropped before they free themselves from the 
sac. In this latter case, upon landing upon the surface of the leaf 
they expand and contract gently until the sac is ruptured at the 
cephalic extremity and they are freed from their prison. 

NUMBER OF GENERATIONS PER YEAR. 

During the summer of 1907, at Richmond, Ind., a study of the 
continuous generations of this species was begun and followed 
through until December 10, the sexual forms and eggs being secured 
from bluegrass in the fields in October. With some of the young 
that hatched from these eggs (stem mothers) March 27 five lines of 
continuous-generation studies were begun and continued until the 
appearance of the sexes and eggs in the fall. These eggs were 
carefully retained and taken to Lafayette, Ind., where, upon their 
hatching on the first day of the following April, two more lines of 
continuous-generation studies were begun and continued until ended 
by the appearance of the sexes and eggs in the fall of 1909, as was 
the case in 1908. 



64 



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70 THE SPRiHG GRAIlST-APHIS OB U GREEN BUG. M 

Mr. T. D. Urbahns, of this bureau, carried on a series of check 
experiments at Dallas, Tex., in 1909, starting in March and ending in 
the fall. (See table, pp. 64-69.) As will be observed, and for 
reasons explained farther on, he did not obtain the sexes. By these 
experiments the maximum number of generations was secured as 
described under rearing methods (p. 51). The maximum number of 
generations in 1908 among the five series of continuous generations was 
21 and, as shown below, occurred in series I of first-born; the mini- 
mum being 6 in series FF of the series of last-born. The complete 
series are as follows: Series B, maximum (from first-born), 20 genera- 
tions; series BB, minimum (from last-born), 9 generations; series C, 
maximum (from first-born), 18 generations; series CC minimum 
(from last-born), 8 generations; series F, maximum (from first-born), 
16 generations; series FF, minimum (from last-born), 6 generations; 
series G, maximum (from first-born), 19 generations; series GG, 
minimum (from last-born), 9 generations; series I, maximum (from 
first-born), 21 generations; series II, minimum (from last-born), 10 
generations. If all of these be added, we will find the average to be 
13.6 generations. This will represent the approximate number of 
generations for the year. In 1909 there were two series reared, A and 
B, both resulting the same. Series A, maximum (from first-born), 
18 generations; series AA, minimum (from last-born), 7 generations; 
series B, maximum (from first-born), 18 generations; series BB, 
minimum (from last-born), 7 generations. The average for these 
two lines would give 12.5 generations, a little lower average than at 
Richmond, Ind. 

Mr. Urbahns carried out one series of first-born generation experi- 
ments at Dallas, Tex., in 1909, from which he obtained only the 
maximum number of generations. He began March 31 and finished 
November 3. In this time he reared through 25 generations but did 
not ascertain the sexes, neither was he successful in finding them in 
the fields. 

It appears that the species will vary in the number of generations 
produced from individuals hatched the same day, and from the off- 
spring kept under the same conditions throughout the year. This 
will readily be understood when the amount of individual variation 
in molting is considered. 

AGE AT WHICH FEMALES BEGIN REPRODUCING. 

The age at which females begin reproducing varies greatly between 
spring and summer and between fall and summer; as between spring 
and fall the age is very much the same. At Richmond and La Fayette, 
Ind., Toxoptera begins reproducing at from 5.9 to 16 days between 
the middle of May and latter part of September. From the time of 
hatching until the middle of May the period is from 20 to 27 days; 



REPRODUCTIVE PERIOD. 71 

from the latter part of September to and including November the 
period varies from 12 to 53 da}^s. A case occurred in the autumn of 
1907 where it required 53 days for a single individual to reach ma- 
turity. This individual continued to live up to the 10th of December, 
when all experiments were closed. The average period from birth to 
reproduction for the summer months, early spring, and early fall is 
9, 22, and 19 days respectively. The average for the entire year, or 
for the period in which, the species breeds, parthenogenetically, for 
Richmond and La Fayette, Ind., is 16.6 days. In arriving at these 
averages, all individuals of the generation experiments for 1907, 1908, 
and 1909 were considered. 

Mr. Urbahns found that at Dallas, Tex., the period varied from 
7 to 12 days from birth to reproduction, from March to the middle of 
May; from 6 to 14 days from the middle of May until the last week in 
September, and from 9 to 11 days from the last week of September to 
November 3 . The average number of days from birth to reproduction 
for each of these periods is 9.6, 7.4, and 9.7 days, respectively. Mr. 
Urbahns reared a number through December up to the middle of 
January. During this period the time between birth and reproduc- 
tion was very much greater, varying from 18 to 25 days, with an 
average of 20.5 days. The average, beginning with April and con- 
tinuing until November 3, is 8.9 days. From the foregoing data it 
will be seen that under favorable conditions Toxoptera breeds much 
more rapidly in the South than in the North. All of the reproduction 
experiments upon which these figures are based were carried on out 
of doors, but the insects were protected from the hot rays of the sun in 
the summer. 

REPRODUCTIVE PERIOD. 

The period of reproduction covers a greater average length of time 
in spring and fall than during summer, being greatest in the spring, 
even though the maximum period of reproduction for a single female 
is practically the same for the three periods. 

In computing these averages each individual of all the lines of con- 
tinuous generations was considered, even though they reproduced for 
a single day only and then died or disappeared from some unknown 
cause; hence the averages are lower than they would be had these 
latter individuals not been considered. From this data it will be 
seen that both the maximum and the average periods are the great- 
est in the North, where the insect is able to breed continuously in 
unprotected places throughout the summer. 

At Richmond and La Fayette, Ind., the maximum period of repro- 
duction for individuals born from March to the middle of June is 45 
days, the minimum 1 day, and the average 18 days; the maximum 
for individuals born from the middle of June to the middle of August 



72 THE SPRING GRAIN-APHIS OR u GREEN BUG." 

is 43 days, the minimum 1 day, the average being 12.6 days; the 
maximum for those born after the middle of August is 45 days and 
the minumum 5 days, the average being 24 days, while the average 
for the entire season is 16 days. 

In Texas the difference between summer, spring, and fall is still 
more marked, December and January being about the same as the 
summer months. Mr. Urbahns found that during December and 
January the maximum reproduction period was 19 days and the 
minimum 2 days, the average being 8 days; during April and May 
the maximum was 30 days and the minimum 4 days, the average 
being 16.8 days; during June, July, and August the maximum was 
16 days and the minimum 4 days, the average being 8.4 days; during 
September, October, and November the maximum was 28 days and 
the minimum 3 days, the average being 17 days. The average for the 
entire season was 13.9 days. 

LONGEVITY. 

At Richmond and La Fayette, Ind., Toxoptera lives for a much 
longer period in the spring and fall than in the summer. In fact, in 
the summer it often survives a shorter time than is required for it to 
reach maturity in the spring and fall. 

Those born from the latter part of March to the last week in May 
live from 15 to 78 days, the average being 43 days; those born from 
the first week in June to the middle of August live from 9 to 57 days, 
the average being 24 days; those born from the middle of August on 
through September live from 12 to 75 days, the average thus being 40 
days. The average length of life for the whole viviparous breeding 
season is 35 days. These averages are not made up from the maxi- 
mum and minimum alone but every individual in the line of first- 
born of the continuous generation experiments is considered. 

Mr. Urbahns found that in Texas the spring grain-aphis lived much 
longer in spring and fall than in summer. In fact, in the summer it 
was difficult to keep it alive at all, it being necessary to keep the cages 
in the shade. 1 He also carried on some reproduction experiments in 
December and January, and in these two months found that it lived 
from 25 to 39 days, averaging 34 days. In April and May it lived 
from 13 to 47 days, averaging 35 days; in June, July, and August it 
lived from 10 to 30 days, averaging 17 days; in September, October, 
and part of November it lived from 11 to 56 days, averaging 28 days; 
the average for the season (from March to November) was thus 26 
days. 

In making up these averages only whole numbers are used, frac- 
tional parts of a day not being considered. Also, all individuals 
upon which we had complete observations were considered. 

i Ante, p. 47. 



THE SPRING GRAIN-APHIS OR U GREEN BUG." 73 

FECUNDITY OF VIVIPAROUS FEMALE. 

The average person, unfamiliar with the habits of the Aphididae, 
would scarcely think it possible for such small creatures to become 
sufficiently numerous to devastate vast areas of grainfields, destroy- 
ing millions of dollars' worth of property within the space of a few 
weeks. When one becomes familiar with their powers of reproduc- 
tion, however, the problem seems very simple. 

Prof. Huxley x states that the tenth generation alone of a single 
rose aphis, were all of its members to survive the perils to which they 
are exposed, would contain more substance than 500,000,000 stout 
men. Buckton, 2 commenting on Prof. Huxley's figures, states that 
he much underestimates the real quantity of animal matter capable 
of elaboration from a single aphis in a year, and goes on to say : 

Basing the calculation, for simplicity, upon the supposition that every aphis lives 
twenty days, and that at the expiration of that period each aphis shall have pro- 
duced twenty young and no more, then at the expiration of three hundred days only, 
the living individuals would be represented by the following figures: 
Aphides. Days. Aphides. 

1 produces in 20 20 = a 

a produces in 40=20 2 400 = 6 

b produces in 100=20 5 3, 200, 000 = c 

c produces in 200=20 10 10, 240, 000, 000, 000 = d 

d produces in 300=20 15 =32, 768, 000, 000, 000, 000, 000 = e 

Again, if 1,000 aphides weigh 1 grain, and 
1 man weighs 2,000,000 grains 
1 man weighs 2,000,000,000 aphides. 

E 
■"■ 9 000 000 000 = 1>638,400,000 men ; equal, perhaps, to the population of China seven- 
fold! 

To quote further: 

But a mathematical friend remarks that this calculation even does not express the 
real rate of increase, since it supposes the progeny of the first aphis to be produced at 
once, and not to commence producing until the expiration of the first twenty days. 
To this same friend I am indebted for the annexed calculation. 

If we suppose the progeny of the first aphis to equal 20 in twenty days, and this 
progeny to begin producing when five days old 20 young, each of which again on 
attaining the age of five days begins the propagation of 20 young, and completes also 
that number in 20 days: 
Then at the end of 20 days from the commencement of first aphis production 

there would be direct issue = 20a 

At the end of fifth day, progeny a begin to produce, which at the end of first 20 

days will altogether equal 15+144-13+12, &C.+2+1 =1206 

At the end of tenth day, progeny 6 begin to produce, which at the end of the 

first 20 days will altogether equal 10+9+8, &c. +2+1 = 55 c 

At the end of the fifteenth day, progeny c begin to produce, which at the end of 

the first 20 days will altogether equal 5+4+3+2+1 = 15c? 

Total at the end of 20 days equals a+b+c+d =210 

The amount, therefore, at the end of 300 days (or 20X15) would not be less than the 
fifteenth power of 210, which is almost impossible to express in figures. There would 
be room in the world for nothing else but aphides. 

» Trans. Linn. Soc., vol. 22, p. 215 (part 3, 1858). « Monograph of British Aphides, vol. 1, p. 80. 



74 THE SPRING GRAIN-APHIS OR " GREEN BUG.'' 

Toxoptera, in all probability, would not fall far behind these 
figures and the number might even be greater. Be that as it may, 
the illustration will suffice to show us that Toxoptera, with such 
remarkable powers of reproduction, could easily overrun the whole 
country if not checked in some manner. 

At Richmond and La Fayette, Ind., the maximum number of 
young produced in 24 hours was 8 in June, July, and August. The 
maximum number of young produced by any individual was 93, in 
the month of July. In Texas Mr. Urbahns found the maximum in 
24 hours to be 10 young in May, and the total number of young for 
one individual reached as high as 84 during the same month. 

At Richmond and La Fayette, Ind., considering the progeny from only 
the individuals of the line of first-born generations, the average num- 
ber of young for the summer falls below either spring or fall, the spring 
being in the lead. When both the individuals from the line of first 
and last born generations are considered, those of the fall average 
less than those of the spring or summer. In 1908 the evidence was in 
favor of the line of first-born generations as being more prolific than 
the individuals of the line of last born. In 1909 the line of last-born 
generations held its own, especially in the spring and summer, falling 
behind slightly in the fall. In fact, in each line of generation experi- 
ments, the last born fall behind in average number of young in the 
autumn. Also, if an average be taken of the first and last born sepa- 
rately, the latter will fall behind. Considering each individual of 
both lines in all generations, both first and last together, the results 
are as follows: The maximum number of young produced by those 
born from March to the middle of June is 69, the average number for 
each individual for this period being 30.3; the maximum for those 
born from the middle of June until the middle of August is 93 young, 
the average number for each individual being 25.3; the maximum 
for those born after the middle of August is 66 young, the average 
for each individual being 24. 

The average number of young, including every individual under 
observation, whether connected with the generation experiments or 
otherwise, for the entire viviparous breeding season, of the years 
1907, 1908, and 1909, beginning the last week in March and continuing 
until November, both inclusive, is 28.2; there being 216 individuals 
used to obtain this average. 

In the generation experiments were a number of individuals that 
produced from 1 to 10 young and then disappeared, apparently not 
dying from natural causes. . All of these were included, however, in 
arriving at the final average, as any average obtained by excluding 
one or more individuals from any cause whatever would be 'more or 
less arbitrary, since in nature the mortality, in all probability, would 
be much greater. All of the rearings were carried on out of doors, 



FECUNDITY OF WINGLESS VS. WINGED FEMALES. 75 

and as the individuals were isolated and protected as much as pos- 
sible from natural enemies it is probably safe to say that this average 
is as high as would obtain in the open fields, where they are convenient 
prey for their enemies. 

Mr. Urbahns found that in Texas the average number of young 
produced in the spring and fall was much greater than in the summer. 
The averages for December and January agree very well with those 
of the summer period. 

The maximum number of young produced by a single individual, 
under observation by Mr. Urbahns, that began reproducing in De- 
cember and January was 29, the average for this period being 17. 1; 
the maximum for those that began reproducing in April and May 
was 84, the average being 58.5 young; the maximum for those that 
began reproducing in June, July, and August was 39, the average 
being 17.2 young; the maximum for those individuals that began 
reproducing after August was 73; the average for the period from 
March to November is 39.7; the average for the entire number of 
individuals upon which Mr. Urbahns made observations during 1909, 
including the rearings during December and January, is 34 young. 
As will be observed, this is considerably above the average for 
Indiana. 

From the foregoing data it will be seen that the spring, in both 
the North and the South, is the most favorable period for reproduc- 
tion; in the North the summer period ranks next, the fall coming 
last, while in the South the summer is so hot that the aphidids can 
scarcely live at all, the fall ranking next to spring for productiveness. 

FECUNDITY OF WINGLESS VERSUS WINGED FEMALES. 

In 1890 the senior author gathered from his observations that the 
wingless forms were more prolific than the winged. In 1907 the 
junior author came to the same conclusion. In 1909 Mr. Urbahns, 
in Texas, observed that the winged forms did not appear to be so 
prolific as the wingless forms. During the summer of 1909, at La 
Fayette, Ind., the junior author carried on some experiments with a 
view of learning, if possible, something definite in regard to this 
matter. For this purpose 8 nymphs with wing pads and 8 larva? in 
the fourth stage were selected and each placed in a separate cage, 
each cage being placed under the same conditions. This experiment 
began on the 30th of August and all individuals became adult about 
the same time. The maximum number of young produced by a 
single winged individual was 44 and the minimum was 10; the maxi- 
mum number of young produced by a single wingless individual was 
61 and the minimum was 4. The total number of young produced 
by the 8 winged individuals was 224, or an average of 28 young for 
each individual; the total for the 8 wingless individuals- was 274, or 



76 THE SPRING GRAIN-APHIS OR u GREEN BUG." 

an average of 34.25 young to each individual. While too small a 
number of individuals was taken to make the result conclusive, it 
plainly indicates that fecundity is greatest among the "wingless 
individuals. 

AVERAGE NUMBER, OF YOUNG PRODUCED DAILY. 

By "the average daily number of^oung produced" is meant the 
daily average for the reproductive period only of each individual. 
At Richmond and La Fayette, Ind., the average number of young 
produced daily for those born from March to the middle of June is 
1.9; the daily average for those born from the middle of June to the 
middle of August is 1.7; the daily average for those born after the 
middle of August is 1.2. These figures, of course, include only those 
individuals in the generation experiments. The average number of 
young produced daily for the entire year is 1.6. The final average 
remains the same when all individuals are considered, irrespective 
of generation experiments. 

From the above it will be seen that the daily average is greatest 
in the spring, the summer coming next, and the fall last. This 
corresponds also to the average total number of young for each indi- 
vidual for these periods. 

Mr. Urbahns found that the average number of young produced 
daily at Dallas; Tex., for those individuals that began reproducing 
during December and January was 1.5; the daily average for those 
that began reproducing during April and May was 3.4; the average 
for those that began reproducing during June, July, and August was 
2.1; the average for those born aft er August was 2.5. These averages 
will be seen to agree proportionately with the average number of 
young produced by a single individual during these periods, with the 
exception of the daily average for December and January, which is 
considerably lower. The average daily number of young for the 
entire breeding season for which Mr. Urbahns has any data is 2. 

From the above data it will be seen that the average daily number 
of young for Texas is far above the average for Indiana. This can 
probably be accounted for from the fact that the reproductive 
period is much longer in the North and the young are distributed 
over a longer period. Also the average number of young for each 
individual is greater in the South. 

SEXUAL FORMS. 

The first young of the sexes in Indiana are apparently born the 
last week in September, the first adults oftentimes appearing as early 
as the first week of October. The adults can be found from this time 
on until December, or until they are killed off by extreme cold. 

The males can easily be distinguished by their small size. The 
oviparous females (fig. 9) can be readily distinguished without a hand 



SEXUAL FORMS. 77 

lens by the yellowish areas over the abdomen, due to the fact that the 
eggs show through the body walls; also, if the males have not been 
with them, by the manner in which they rest upon the plant, the 
body being held at an angle of about 45° to the leaf upon which they 
rest. In assuming this position they hold to the plant only with the 
two first pairs of legs. Only unmated females rest upon the plant 
in this manner. The sexes may mate once or many times, although 
one mating is apparently sufficient to produce fertile eggs. 

One agamic female may produce all agamic individuals, a com- 
bination of agamic males and oviparous females, or only true females 
and males. When only the latter, it seems that the females far 
outnumber the males. 

Mr. C. N. Ainslie, in 1908, in Washington, D. C, records a very 
singular phenomenon. On April 4 of that year he observed males ; 
oviparous females, and eggs of Toxoptera in his cages in the office. 
A number of eggs were obtained, but none of them would hatch. The 
source of this material, however, is somewhat obscure. Mr. Kelly 
had sent in material from Leavenworth, Kans., previous to these 
finds and this was kept breeding in the office, together with material 
collected locally. The junior author also found an adult male in his 
rearing cages in the insectary at Waslrington during April, 1911. 
This apparently developed from material that had been kept breed- 
ing all winter. 

DESCRIPTIONS. 

Since in the earlier stages the young can not be distinguished from 
those of the summer forms, it is unnecessary to go into detail with 
reference to them. The males may probably be identified in the 
third instar by their small size; they are much smaller and the abdo- 
men more pointed, posteriorly, than the summer forms of this stage 
that later will become winged. Those young that will develop into 
oviparous females can not be determined with any degree of accuracy 
until the fourth instar. They are usually a little paler in color, and, 
instead of embryos, light yellowish ova can be seen, with a hand 
lens, developing within the body (see fig. 9). The description of 
the male and female first appeared in the Canadian Entomologist, 
in an article on " Sexual Forms of Toxoptera graminum, Rond," by 
Prof. F. L. Washburn. 1 His description is as follows: 

Oviparous female. — Length, 2-2.25 mm.; color, yellowish green, median line of 
abdomen darker green; head and prothorax somewhat paler than the rest of the body. 
Eyes black; antennae black, except the two basal joints, and the basal half of the 
third, which are the same color as the head. Legs yellowish, tibia brownish toward 
the apex, tarsi black; cornicles greenish, their apex black; cauda greenish. Antennae 
slender, hardly one-half the length of the body, no circular eensoria. Cornicles 
slightly tapering, not reaching to the end of the body. Cauda slender, somewhat 

i Can. Ent., vol. 40, No. 2, February, 1908. 



78 

constricted above the middle, about two-thirds the length of the cornicles. Tibia 
of hind leg (fig. 10) swollen and thickly covered with sensoria-like swellings. Lateral 
tubercles small and single. 

Winged male. — Expanse of wings about 4.5 mm.; length of body about 1.3 mm. 
General coloration of the abdomen yellowish green; head brownish-yellow; eyes 
black; antennas black, except the two basal joints and the proximal half of the third, 
which are yellowish green. Legs yellow, the femora more or less dusky, the posterior 
pair darkest; apex of the tibia and tarsi black; cornicles yellowish, with black apex; 
cauda yellowish. Wings, costa and subcosta yellow; stigma paler, the inner edge of 
the stigma and the veins black. Antennas long and slender, reaching to or a little 
beyond the end of the body; third joint with about twenty circular sensoria; fourth 
with about eighteen; fifth with about nine. Cauda slender, somewhat constricted 
about the middle, as long as the cornicles. Lateral tubercles small and single. 

To this description we add the following: 

Oviparous female. — Measurements of antennal joints (average from eight indi- 
viduals): I, 0.067 mm.; II, 0.050 mm.; Ill, 0.229 mm.; IV, 0.166 mm.; V, 0.172 mm.; 
VI, base 0.095 mm.; VI, filament, 0.369 mm.; total length, 1.148 mm. 

Male (average from six individuals) (fig. 6): 1,0.064 mm.; II, 0.051 mm.; Ill, 0.361 
mm.; IV, 0.243 mm.; V, 0.242 mm.; VI, base, 0.107 mm.; VI, filament, 0.407 mm.; 
total length, 1.475 mm. 

We find also that the coloration of the oviparous female varies 
considerably from almost a clay-yellow with a faint tinge of green 
to a deep green. Individuals are somewhat pruinose also. As they 
become older the legs and bases of the antennas get darker; each 
margin of the base of the cauda becomes quite dark. 

The abdomen of the male varies somewhat in color from deep 
apple-green to pale green ; the thoracic plates, dorsally and ventrally, 
arc- of an olive color. 

MOLTING. 

As stated on page 62 Mr. Vickery, of this bureau, conducted some 
experiments at Richmond, Ind., in 1908, to ascertain the number of 
molts for the sexes. He selected 6 individuals just as they were 
born and isolated each in cages as heretofore described. Three 
proved to be males and 3 oviparous females, all of which molted 
4 times. Also, at La Fayette, Ind., in 1909, the junior author found 
that the oviparous forms molted 4 times. 

OVIPAROUS DEVELOPMENT. 

AGE AT WHICH FEMALES BEGIN OVIPOSITION. 

The age at which females begin depositing eggs varies greatly 
according to weather conditions. From 11 to 41 days are required 
for them to become adult. If they happen to be born the last week 
in September or the first week in October the chances are that they 
will become adult within about 11 days. If they have the misfor- 
tune to be born the last week in October or during November it 
may take them over a month to reach maturity; perhaps they would 



PERIOD OF OVIPOSITION. 



79 



not reach maturity at all in case of an early winter. After reaching 
maturity they will, when accompanied by the male, begin ovipositing 
in from 3 to 9 days; if the weather is warm, in from 3 to 4 days. 
The period, then, from birth to oviposition varies from about 14 to 
44 or 4.5 days. Females will, in rare instances only, oviposit without 
first having been with the male. They will live unfertilized from 31 
to 71 days without ovipositing, the abdomen becoming very much 
distended, and, upon dissection, 6 or more fully developed eggs may 
be found. In one case a female deposited 2 eggs without having 
been with a male, but no development occurred within the egg and 
it shriveled and dried up within a few days. When nearly through 
ovipositing the female becomes shrunken and misshapen, as shown 
in figure 15. (Compare with fig. 9.) 

PLACE OF OVIPOSITION. 

Throughout the North it ap- 
pears that bluegrass (Poa pra- 
tensis) is the most common host 
plant of Toxoptera, though it 
occasionally, on account of favor- 
able weather conditions or the 
scarcity of natural enemies, be- 
comes excessively abundant there 
and escapes to the grains in 
destructive numbers. Conse- 
quently it appears that the sexes 
normally occur on bluegrass. It 
is also true that they will be bet- 
ter protected from the extremes 
of temperature among tall, rank growing bluegrass than they would 
be on the grains in open, bleak fields. 

In only a very few instances have we been able to find the sexes 
upon the growing grains in the fields. It is an easy matter, how- 
ever, to locate them upon bluegrass in waste places. They appar- 
ently prefer dead or dying leaves and crawl out near the tip of the 
leaf, where it has begun to fold, and here deposit their eggs. (See 
fig. 11.) Several old females have been found at the same time 
within the curl of a leaf, and as many as 14 eggs have been found 
upon a single leaf. 

PERIOD OF OVIPOSITION. 

Here again, as in the case of viviparous development, varying 
temperatures are probably the main factor in determining the length 
of the productive period. Eggs continue to develop within the 
bodies of the females, apparently, as the embryos do within the 




Fig. 15.— The spring grain-aphis: Shrunken and nearly 
spent oviparous female. Enlarged. (Original.) 



80 THE SPRING GRAIN-APHIS OR 

bodies of the viviparous individuals, so long as warm weather con- 
tinues or until the females become old and die a natural death. The 
viviparous forms appear to be as susceptible to extreme cold as are 
the oviparous individuals. 

From the 14 experiments that were conducted to determine the 
period of oviposition it was found that it varied from 3 to about 25 
days. If, after becoming adult, the female be kept for a week or more 
and then placed with the male it appears that the reproductive period 
is shortened. 




Fig. 16.— The spring grain-aphis: Aberrant female with eggs and embryos in abdomen, showing through 
the body wall. Enlarged. (Original.) 

LENGTH OF LIFE OF THE SEXES. 

The males reach maturity, it seems, as quickly as the oviparous 
females, but their lives are much shorter. The males live from 8 to 10 
days after becoming adult. 

The length of life of the oviparous females depends principally 
upon two factors, namely, weather conditions and the presence of the 
male. Under favorable weather conditions, and in the presence of the 
male, they will live from 31 to 68 days. If the male is not present 
they will sometimes live as long as 88 days. Under these circum- 
stances they rarely deposit eggs, only one instance, as previously cited, 
having come under our observation where they did oviposit and then 
the eggs were not fertile. Their abdomens become greatly distended 
with eggs, and upon being dissected, as many as six or more full-sized 
eggs may be found. 



INFLUENCE OF WINDS ON DIFFUSION. 



81 



FECUNDITY OF OVIPAROUS FORMS. 

The oviparous forms are far less prolific than the viviparous. They 
produce, under favorable circumstances, from 1 to 10 eggs, or an 
average of 5.4 eggs per individual. This average was made up from 
observations on 27 individuals. 

ABERRANT INDIVIDUALS. 

During our studies of Toxoptera we have found some rather inter- 
esting abnormalities. In December, 1907, 1 while dissecting some 
individuals in the laboratory, two were found that contained both 
living embryos and true eggs. In April, 1908, Mr. C. N. Ainslie found 
the same phenomenon occurring in 
individuals here in Washington. 
These latter resembled the wingless 
viviparous forms externally (see fig. 
16). Mr. S. J. Hunter, in "The 
Green Bug and Its Enemies," finds, 
besides this form, what he terms 
"winged intermediate females, re- 
sembling the winged agamic females 
in antenna! characteristics." Other 
writers mention the same phenom- 
enon as occurring among other species 
of plant-lice, and no doubt these abnor- 
malities occur much oftener than any 
of us are aware. At present, however, 
there appears to be no satisfactory 
explanation of such occurrences. 

One single instance came under our observation where a puparium 
produced 6 young and then died. The cauda of this individual 
resembled that of an adult insect and the wing-pads were aborted, 
the abdomen being much broader than that of the normal pupa. 
(See fig. 17.) 

INFLUENCE OF WINDS ON DIFFUSION. 

By referring to the maps (fig. 5) showing the area covered by the 
different outbreaks of Toxoptera in the United States, west of the 
Mississippi River, it will be observed that they have all had their 
origin in central Texas, with a single exception, extending broadly to 
the north and northeast. Tins was especially true of two most des- 
tructive invasions of 1890 and 1907, and was also implied by that of 
1901, the case of 1903 having been too incipient. This strongly indicates 




Kprr 



Fig. 17.— The spring grain-aphis: Aberrant 
female pupa which produced young. En- 
larged. (Original.) 



26675° 



» Proc. Ent. Soc. Wash., vol. 10, pp. 11-13, January, 1908. 
-Bull. 110—12 6 



5~ THE SPBTXG GRAIX-APHIS OK "GREEN BUG." 

the presence, during each extended invasion, of sonic important influ- 
ence that shapes, to a marked degree, the course of these invasions 
across the country northward and northeastward froni the point of 
their origin in the South. Probably this is due primarily to the direc- 
tion of the winds during the months between January and June. 
The degree of influence exerted by the winds in the diffusion of 
ptera is. however, dependent upon s :her factors. In the 

~ith wingless individuals alone present, it is clear that no 
amount of wind of whatever vel fistrih 

; ^nsdderahle degree. Therefore, it is necessary to understand the 

vital forces that regulate the abundance of winged indivi zich, 

at the critical period, would probably be almost without exception 

viviparous females. Field ol — : have shown, not only among 

this but among other species of aphidids, that a curtailing of the food 

supply is a most potez: influence in producing the aerial form. N : 

only has i: been observed with Toxoptera that as the food pi 

their vig affording less nulriliqm, the winged individuals become 

zz:r- ~.z£ zz :zzz:zzt zz :j_f Zt~_:'s V . : *" :L __": I " """:? ;zzz Mr. 

hn h vt He by regulating the food suz produce 

these winged individuals . artificiafly at wfll. in their rearing cages. In 

the case of Maerosiphum $ruriartaBuckt..it has always been noticed 

that though the heads of wheat be literally swarming with wingless 

females and young these young do not pz :he food supply 

becomes exhausted on account of the ripening of the grain, but 

levelop into winged adults which fly away, leaving only the cast larval 

_ :;:i -izzs z :: - z zzzz^ ~i:Z _z"zz TL-z'zzre s 1 zr :.- 

there is an abundant supply of vigorous young grain the percent ^ g 

wmg . __ : ■ zi" aratively few. The conditi 

zze food supply, then, is a prime fac: : in :_t zzzjzizn of Toxoptera. 

7"zz~Lzz- - zz : z:.._':::.: zz::-Z:Z.:zzz, 

K—tTtZz zelow the pziz: ecies.it 

ry dear that the velocity of the wind would have no effect what- 

- zipon the diffusion of the insect. The conditions necessary, then, 

for the wind to exert its greatest influence will be a decreasing food 

supply for the insect under a temperature considerably above that 

actually necessary for its activity, with numbers not seriously reduced 

under these conditions, many species of aphidids are 

known to be carried about in immense numbers by the winds. 

White in hk Natural History of Selborne ■ has this reference to 
a migration of small aphidids. 

- . • ■ 

i -: :: ------ -■■_-_:■; z. .- zzz_zz-z I --__"_ 1 i. -:-. — -- ~. z. : - riiUT: : z. : zz-Z.1'. 

.---'— i=r~ - '_: 1 — : - --_t ■-- : i- ~~z_- - 'i^:- : - : ~. ' -z. r - '. z.z-: :■ _■ : , - A _r_f- 1. 

fhe Err. Gilbert White, M. A., Loodon,1^6,pp. 



IXFLUE 

ibout three o'clock in'the afternoon of that day, which was very hot, the people 

of this village were surprised by a shower of Aphides, or smother-flies, which fell in 

Those that were walking in the street at that juncture found themselves 

red wiih these insects, which settled also on the hedges and gardens, blackening 

all the vegetables where they alighted. My annuals were discoloured with them, and 

ilks of a bed of onions were quite coated over for six days after. These armies 

were then, no doubt, in a state of emigration, and shifting their quarters; and might 

have come, as far as we know, from the great hop plantations of Kent or Sussex, the 

wind being all that day in the easterly quarter. They were observed at the same 

time in great clouds about Faraham, and all along the vale irom Faraham to Alton. 

Prof. Karl Sajo calls attention to the fact that many aphidids creep 
e crowns f the plant which they infest and then drop them- 
s at the proper moment into the boiling current of the storm. 1 
In the studies made of Toxoptera many instances of this nature 
have been observed. It will be recalled that Toxoptera araminum 
appeared in swarms about Parma. Italy, in 1S47 and again in 1852. 
The notes of Mr. C. X. Ainslie, made on Toxoptera in Oklahoma 
and Kansas, contain very many similar interesting recc : - 

At Kingfisher, Okla., under date of March 27 1907, XLr. Ainslie 
makes this record. 

Toxoptera flying to-day by the million. The air was full of the migrants, and 
farmers who drove to town were covered on the windward side to their annoyance. 
The aphides seem for the most part to fly low, but the wind hurried them at such a 
rapid rate that they might easily have been invisible when higher in the air. 

The following day his field notes contained these significar: si 
ments: 'Large numbers of Toxoptera on the wing to-day, al 
moving north," and as those who have studied the species will 
understand, the most interesting stateme::; was that "A 1:-. 
thunder shower passed by on the north last night. 30 miles away, 
and a few drops fell here."' In the same locality, under date of 
April 3, he states that winged individuals of Toxoptera were taking 
wing freely, for he had observed many leaving the blades in the 
fields and taking flight. Again, under date : A rfl 6, '"The a 
full of flying Toxoptera to-day, going northeast with a light breeze. 
They do not fly high, from 2 to IS feet.'" (The temperatui 
Wichita, 30 miles north, was from 42° to 57° FJ At Wellington, 
Kans., April 24 (with Wichita temperature 45° to 81° F.). he found 
Toxoptera flying by the million and fanners driving : wn had to 
shelter their eyes from the swarm. On April 29. he records these 
observations: 

Yesterday afternoon was warm for awhile (41° to 63° F. at Wichita ', light north- 
breeze. Toxoptera took wing in immense numbers f : drift- 
ing southwest, but soon saw their mistake and the air dewed. This is the 
instance seen by me when these aphides failed to fly north. The wind did not 
them far this time. A Sunday ball game was in progress when they flew, and I WW 
told that the myriads of aphides interfered with the game: it was like trying to play 
in a snowstorm . 

» The Wanderings of Insects. Prometheus , vol. 1, bj Prof. Karl - 



84 

Under date of May 17, 1907, also at Wellington, Kans., Mr. Ainslie 
made an interesting record as follows: 

Yesterday, the 16th, the air was full of Toxoptera rising on wing, but the breeze 
was light and they had no chance to travel far. If the wind had favored their flight 
they must have carried parasites with them as guests, by the myriad, for many of 
them, probably the major part, were parasitized. [The temperature at Wichita 
ranged from 44° to 82° F.] 

On the same day the senior author, in company with Prof. E. A. 
Popenoe, in driving about the country in the vicinity of Manhattan, 
Kans., during the afternoon found that they were in the midst of 
swarms of winged Toxoptera; frequently a number of individuals 
might be noted crawling about over their hats and coats and to an 
annoying degree traveling over their faces. Two days later, the 
senior author observed both winged Toxoptera and Aphidius crawl- 
ing about on the inside of the windows of a Pullman car in which he 
was traveling over the Santa Fe, crossing central Kansas. 

At Piano, Tex., June 4, 1909, Mr. Urbahns learned of a most 
interesting migration reported to him as having taken place two 
days before. A farmer, Mr. Foreman, reported to him that " green 
bugs" were observed flying east, probably coming from out of a 
very badly infested wheat field, moving with the evening breeze. 
In this case there was clearly a rapid disappearing of the food supply, 
precipitating a development to winged adults that were probably 
forsaking the fields for some other locality affording them a greater 
abundance of food. It would appear, then, that the influence of 
winds is more or less dependent upon several other phenomena. 

With the natural advance of spring from the South, there would 
be a continually decreasing supply of fresh, tender, succulent food 
in the South, while to the North this condition would be reversed. 
Therefore, with winged viviparous females developing with increas- 
ing abundance along the area of a certain latitude, such winged 
females as were carried south or backward over an area already ren- 
dered barren of food would consequently perish. On the other 
hand, those females that drifted or made their way northward would 
encounter a continually increasing fresh supply of food; therefore 
they might be said to follow along with the advance of the spring 
from the South far into the North, until overtaken by their natural 
enemies. Then, too, south winds are associated with a warm tem- 
perature and north winds with the reverse, as will be seen from 
Tables IV- VIII, furnished by the United States Weather Bureau. 
Another factor that must not be lost sight of is that after about the 
latitude of southern Kansas and Missouri is reached wheat ceases 
to be the food plant for Toxoptera in spring, and spring oats takes 
its place in this respect. 



INFLUENCE OF WINDS ON DIFFUSION. 



85 



Still another factor of greatest importance is in the fact that, 
with a wind from a southern quarter, blowing strongly under a tem- 
perature sufficient to render Aphidius active, both Toxoptera and 
parasite would thus be carried on the wing perhaps miles to the 
northward and scattered over fields not previously seriously infested. 
The following day, or some days after, there might come a north wind 
with greatly reduced temperature, which, though not sufficiently 
cold to prevent immediate reproduction on the part of migrant 
Toxoptera, would yet keep the parasite inactive. That precisely 
these weather conditions do often occur during years of excessive 
abundance of Toxoptera is shown by the following tables of the 
weather (Tables IV- VIII), while the dates thereof show conclu- 
sively that both Toxoptera and Aphidius were present and active. 
This last factor will be further discussed under natural enemies. 
These tables were compiled for us by the Weather Bureau. 

Table IV. — Maximum and minimum temperatures, ivith direction and velocity of wind, 
and character of the day, San Antonio, Tex., 1907. 











Di- 


Ve- 










Di- 


Ve- 


Date 
(1907). 


"Weather. 


Maxi- 
mum. 


Mini- 
mum. 


tion 

of 

wind . 


loci- 
ty of 
wind. 


Date 
(1907). 


Weather. 


Maxi- 
mum. 


Mini- 
mum. 


tion. 

of 
wind . 


loci- 
ty of 
wind. 












Miles 












Miles 












per 












per 






°F. 


°F. 




hour. 






°F. 


°F. 




hour. 


Feb. 1 


Clear . 


81 
83 
49 
56 
47 
43 
60 
6S 
73 


63 
48 
38 
33 
28 
34 
39 
33 
38 


SE. 

N. 

N. 
NE. 
NE. 
NE. 

N. 

N. 

S. 


11 
26 

22 
20 
19 
15 
22 
"7 
15 


Mar. 3 
4 
5 
6 
7 
8 
9 
10 
11 


Clear 


80 
82 
84 
85 
84 
82 
80 
80 
85 


49 
56 
64 
* 64 
64 
66 
66 
57 
65 


SE. 
SE. 

S. 
SE. 

S. 
SE. 

S. 

w. 

SE. 


13 


2 


Fair : 


do 

Fair 


15 


3 


Cloudy 

Pair 


16 


4 


do 

Clear 


18 


5 


do 

Cloudy 

Fair 


15 


6 


Fair 


18 


7 


do 

do 

do 


16 


8 


Clear 


23 


9 


do 


21 


10 


do 


68 


42 


N. 


22 


12 


do 


87 


65 


s. 


21 


11 


....do 


72 


44 


N. 


10 


13 


do 


80 


70 


NE. 


17 


12 


do 


74 


36 


S. 


10 


14 


do 


70 


47 


N. 


36 


13 


do 

do 


78 
71 


46 
50 


s. 

N. 


15 

24 


15 
16 


Clear 


70 
76 


42 
46 


NE. 
SE. 


23 


14 


do 


14 


15 


do 


70 


40 


N. 


9 


17 


do 


88 


66 


SE. 


18 


16 


do 


77 


44 


BW. 


11 


18 


do 


88 


64 


SE. 


15 


17 


do 


80 


48 


SE. 


10 


19 


do 


89 


62 


SE. 


15 


18 


Fail- 


80 
76 
79 


53 
52 
44 


sw. 

N. 
SW. 


14 
IS 
10 


20 
21 
22 


...do 

do 

do 


89 

88 
87 


63 
63 
64 


SE. 
SE. 

SE. 


17 


19 


Clear 


24 


20 


do 


20 


21 


do 


80 


47 


s. 


17 


23 


....do 


86 


66 


S. 


15 


22 


Fair 


80 


52 


SE. 


19 


24 


do 


88 


67 


SE. 


16 


23 


Cloudy 

do 


79 
67 


62 
56 


SE. 

NE. 


15 

22 


25 
26 


Fair 


87 
86 


68 
68 


SE. 
SE. 


18 


24 


do 


20 


25 


do 


66 


48 


N. 


19 


27 


do 


88 


69 


SE. 


17 


26 


do 


68 


49 


SE. 


7 


28 


do 


88 


68 


SE. 


20 


27 


Fail- 


81 


63 


S. 


15 


29 


Cloudy 


73 


55 


N 


26 


28 


do 


80 


64 


N. 


30 


30 


Fair 


72 


55 


N. 


14 


Mar. 1 


Clear 


73 

77 


52 

43 


NW. 

S. 


27 
14 


31 


Clear 


70 


52 


N. 


22 


2 







86 



THE SPRING GRAIN-APHIS OR 



Table V. — Maximum and minimum temperatures, with direction and velocity of wind, 
and character of the day, Fort Worth, Tex., 1907. 



Date 
(1907). 



Feb. 



Mar. 1 



Weather. 



Fair 

Cloudy 

do 

do 

Fair 

do 

do 

Clear 

do 

Fair 

Clear 

do 

do 

do 

....do 

....do 

Fair 

....do 

Clear 

....do 

Fair 

....do 

....do 

....do 

Cloudy 

Fair 

Cloudy 

do 

Clear 

....do 



Maxi 
mum 



Mini- 
mum 



Di- 
rec- 
tion 
of 

wind 



SW. 
NW. 

N. 
NW. 
NE. 
NE. 

N. 

S. 

S. 
NE. 

S. 
SW. 
SW. 

N. 
SW. 
SW. 

s. 

NW. 
N. 

s. 

SW. 
E. 

s. 

NW. 

NE. 
SE. 
SE. 

NW. 
NW. 
SW. 



Ve- 
loci- 
ty of 
wind. 



Miles 
per 

hour. 
16 
30 
17 
16 
12 
9 
23 
" 20 
17 
21 
16 
22 
22 
20 
17 
15 
20 
32 
16 
15 
25 
16 
25 
23 
12 
18 
17 
2S 
24 
23 



Date 
(1907). 



Mar. 3 
4 
5 



Weather 



Clear 

do 

Fair 

do 

do 

do 

do 

Clear 

Fair 

....do 

Clear.... 

....do 

....do 

do 

Fair 

Clear 

....do 

....do 

....do 

....do 

Fair 

....do 

Clear 

Fair 

....do 

....do 

Cloudy 

Clear 

do 



Maxi- 
mum 



Mini- 
mum 



Di- 
rec- 
tion 
of 
wind 



SW. 

SW. 
SW. 
SW. 
NE. 
SW. 

N. 

S. 
SW. 

s. 

N. 

SE. 
SW. 
SW. 
SW. 
SW. 

s. 

SW. 

s. 
s. 
s. 

SW. 

SW. 
SW. 

s. 

NW. 
NE. 

NE. 



Ve- 
loci- 
ty of 

wind. 



Miles 
per 

hour- 
20 
28 
22 
23 
22 
17 
23 
16 
35 



Table VI. — Maximum and minimum temperatures, with direction and velocity of uind, 
and character of the day, Oldahoma City, OMa., 1907. 



Date 

(1907). 



Mar. 



Weather. 



Clear 

....do 

....do 

Cloudy 

do 

....do 

Fair 

Cloudy 

do 

Fair 

Cloudy 

Fair 

Cloudy 

Fair 

....do 

....do 

....do 

....do 

....do 

Clear 

....do 

....do 

Fair 

Cloudy 

Fair 

Cloudy 

do 

....do 

Fair 

....do 

Cloudy 



Maxi- 
mum 



Mini- 
mum, 



Di- 
rec- 
tion 
of 
wind 



N. 
S. 
N. 
E. 
NW. 
N. 
S. 
S. 
N. 
N. 
S. 
S. 
S. 
S. 

s. 
s. 
s. 
s. 
s. 
s. 
s. 



Ve- 
loci- 
ty of 
wind. 



Miles 
per 

hour. 
30 
35 
23 
36 
36 
38 
34 
25 
47 
35 
36 



Date 
(1907). 



Apr. 1 
2 
3 
4 



Weather. 



Fair 

....do 

....do 

Cloudy 

do 

....do 

Clear 

....do 

Fair 

Clear 

...do 

Fair 

....do 

Cloudy 

....do 

....do 

....do 

Fair 

Cloudy 

do 

....do... 

....do 

Clear 

Fair 

Cloud v 

Clear.". 

Cloudy 

Fair 

Cloudy 

Fair..' 







Di- 


Maxi- 


Mini- 


rec- 
tion 
of 


mum. 


mum. 






wind. 


°F. 


°F. 




66 


38 


S. 


75 


48 


S. 


88 


58 


SW. 


68 


54 


N. 


58 


42 


N. 


72 


48 


SE. 


71 


47 


N. 


63 


44 


N. 


79 


41 


W. 


74 


43 


s. 


72 


52 


N. 


58 


42 


N. 


57 


33 


NE. 


61 


44 


S. 


85 


49 


SE. 


64 


34 


NE. 


54 


34 


SE. 


'65 


41 


SE. 


52 


39 


N. 


48 


36 


NE. 


51 


44 


NE. 


46 


40 


N. 


69 


36 


S. 


79 


52 


S. 


64 


40 


N. 


66 


35 


NE. 


80 


55 


S. 


77 


51 


SE. 


64 


34 


N. 


50 


32 


N. 



Ve- 
loci- 
ty of 
wind. 



Miles 

per 

hour. 

34 

52 

43 



INFLUENCE OF WINDS ON DIFFUSION. 



87 



Table VII. — Maximum and minimum temperatures, with direction and velocity of wind, 
and character of the day, Wichita, Kans.,from Mar. 20 to May 31, 1907. * 



Date 

(1907). 


Weather. 


Maxi- 
mum. 


Mini- 
mum. 


Di- 
rec- 
tion 
of 
wind. 


Ve- 
loci- 
ty of 
wind. 


Date 

(1907). 


Weather. 


Maxi- 
mum. 


Mini- 
mum. 


Di- 
rec- 
tion 
of 
wind. 


Ve- 
loci- 
ty of 
wind. 


Mar 20 


Clear 

do 

Fair 


°F. 

67 
91 
92 
78 
85 
89 
78 
69 
79 
68 
68 
57 
65 
71 
81 
71 
60 
57 
62 
60 
74 
63 
66 
55 
53 
52 
74 
51 
58 
53 
53 
52 
58 
56 
73 
81 
53 


°F. 
51 
63 

63 
64 

54 
62 
69 
47 
52 
39 
42 
39 
37 
49 
56 
44 
39 
42 
44 
41 
35 
39 
44 
36 
28 
36 
46 
29 
25 
36 
32 
37 
34 
43 
36 
45 
36 


SW. 
SW. 
SW. 
SW. 

s. 

SW. 
SW. 
SW. 

w. 

NW. 

N. 
NE. 

S. 

S. 
NW. 
NE. 
NE. 

W. 

W. 

N. 

N. 
SE. 
NW. 
NW. 

N. 

SE. 

N. 
NE. 

SE. 

N. 

N. 
NE. 

N. 

S. 
SW. 
SW. 
NE. 


Miles 
per 

hour. 
16 
24 
24 
21 
19 
24 
28 
17 
30 
15 
21 
17 
24 
30 
24 
26 
20 
15 
23 
30 
23 
16 
23 
26 
13 
22 
IS 
22 
14 
25 
14 
14 
9 
11 
17 
34 
24 


Apr. 26 

27 

28 

29 

30 

May 1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 


Clear 


°F. 
63 
77 
63 
41 
49 
61 
67 
51 
50 
50 
51 
57 

. 66 
72 
79 
80 
82 
79 
53 
66 
82 
90 
86 
71 
79 
85 
85 
86 
75 
82 
65 
66 
54 
59 
61 
65 


°F. 
31 
48 
41 
32 
30 
31 
45 
30 
28 
43 
45 
46 
50 
49 
51 
52 
60 
50 
37 
33 
44 
60 
58 
58 
50 
61 
65 
66 
64 
55 
48 
37 
54 
69 
61 
65 


SE. 
SE. 

N. 

N. 

N. 
SW. 

E. 

N. 
SE. 
NE. 
NW. 

N. 

N. 
SE. 
NE. 
SE. 

S. 

S. 

N. 
NW. 

S. 
SW. 
SW. 
NE. 
SE. 
SW. 
SW. 
SE. 
SW. 
NW. 

N. 

N. 
SW. 

E. 

N. 

N. 


Miles 
per 
hour. 
13 


21 


Fair 


19 


22 


Cloudy 

do 

Fair 


18 


23 

24 


Clear 

do 

do 

Cloudy 

Fair 


27 
16 


25 
26 


Clear 

Fair 


9 
14 


27 


Cloudy 

Fair 


27 


28 


Cloudy 

Clear 


15 


29 


Cloudy 

do 

do 

Fair 


13 


30 


Fair 


15 


31 
Apr. 1 


do 

Clear 


9 
12 


2 


Fair 


do 

do 

Clear 

do 

Cloudy 

do 

Fair 


9 


3 
4 


Clear 

Fair 


11 
20 


5 
6 

7 
8 


do 

Cloudy 

do" 

Clear 

do 

Fair 


35 
24 

27 
22 


9 
10 


Clear- 

Fair 


16 
19 


11 
12 


Clear 

do 

Fair 


Cloudy 

Fair 


12 

14 


13 


Clear 

Fair 


16 


14 


Cloudy 

Fair 


24 


15 


Clear 

Fair 


25 


16 


Clou J v • 

Fair 


18 


17 


Cloudy _ 

Fair 


17 


IS 


do 

do 

Cloudy 

do 

do 

Clear 

do 

Fair 


14 


19 
20 


do 

Clear 


26 
14 


21 
22 
23 
24 

25 


Cloudy 

do 

do 

do 


16 
10 
13 
21 



Table VIII. — Maximum and minimum temperatures with direction and velocity of wind, 
and character of the day, Dodge City, Kans..,from Mar. 20 to May 31, 1907. 



Weather. 



Fair 

do 

....do 

Clear 

....do 

Fair 

....do 

....do 

....do 

Clear 

Cloudy 

Fair 

Clear 

Fair 

Clear 

Cloudy 

Fair..*. 

....do 

Clear 







Direc- 


Ve- 




Maxi- 


Mini- 


tion 


locity 


Date 


mum. 


mum. 


of 
wind. 


of 

wind. 


(1907). 








Miles 










per 




°F. 


°F. 




hour. 




91 


41 


SE. 


24 


Apr. 8 


94 


54 


SW. 


28 


9 


89 


43 


S. 


28 


10 


76 


53 


NW. 


23 


11 


86 


46 


S. 


26 


12 


89 


46 


SE. 


30 


13 


85 


54 


SE. 


36 


14 


61 


38 


NW. 


16 


15 


74 


44 


SE. 


35 


16 


62 


30 


NW. 


24 


17 


59 


31 


NW. 


18 


18 


55 


34 


SE. 


16 


19 


72 


36 


SE. 


28 


20 


85 


51 


E. 


23 


21 


73 


49 


NW. 


22 


22 


58 


38 


N. 


15 


23 


61 


26 


SE. 


10 


24 


67 


39 


W. 


25 


25 


66 


33 


SW. 


12 


26 



Weather. 



Fair... 
Clear. . 
....do. 
....do. 
Fair... 
Clear. . 

...do. 
Fair... 
Cloudy 
Clear. . 
Fair... 
Cloudy 

do. 

...do. 
Fair... 
Clear. . 

...do. 
Cloudy 
Fair... 







Direc- 


Maxi- 


Mini- 


tion 


mum. 


mum. 


of 
wind. 


°F. 


°F. 




63 


41 


NW. 


73 


40 


NW. 


77 


37 


SE. 


64 


38 


NW. 


59 


35 


NW. 


55 


28 


E. 


68 


35 


SE. 


70 


39 


NW. 


48 


24 


NE. 


60 


24 


SE. 


51 


32 


NW. 


45 


30 


NE. 


46 


33 


NE. 


48 


28 


SE. 


56 


35 


SE. 


78 


30 


SE. 


76 


36 


W. 


44 


31 


NW. 


64 


28 


SE. 



Ve- 
locity 

of 
wind. 



Miles 
per 

hour. 
23 
16 
27 
24 
15 
13 
26 
23 
14 
16 
18 
10 
9 
10 
9 
18 
24 
17 
18 



88 

Table VIII. — Maximum and minimum temperatures with direction and velocity of wind, 
and character of the day, Dodge City, Kans.,from Mar. 20 to May 31, 1907 — Contd. 



Date 
(1907). 


Weather. 


Maxi- 
mum. 


Mini- 
mum. 


Direc- 
tion 
of 
wind. 


Ve- 
locity 

of 
wind. 


Date 
(1907). 


Weather. 


Maxi- 
mum. 


Mini- 
mum. 


Direc- 
tion 
of 
wind. 


Ve- 
locity 

of 
wind. 


Apr. 27 

28 


Clear 


°F. 

81 
59 

42 
45 
62 
67 
38 
57 
48 
50 
60 
68 
71 
78 
84 
90 
70 
55 


°F. 

37 
32 
25 
20 
37 
32 
27 
27 
41 
42 
40 
43 
49 
45 
48 
60 
39 
34 


N. 

N. 

N. 
NW. 

SE. 
NW. 
NW. 

SE. 

SE. 
NE. 

E. 

N. 

E 
NW. 

SE. 

SE. 
NW. 
NW. 


Miles 
per 
hour. 
16 
16 
18 
7 

12 

18 

20 

22 

8 

7 

8 

6 

10 

5 

24 

31 

17 

16 


May 15 
16 
17 

18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 


Clear 


"F. 

67 
86 
92 
81 
73 
81 
86 
88 
87 
78 
74 
62 
64 
52 
58 
59 
67 


°F. 

30 
42 
53 
55 
50 
50 
60 
65 
64 
55 
47 
37 
30 
42 
46 
49 
48 


W. 

SE. 
SE. 

NE. 

N. 
SE. 
SE. 
SE. 
SE. 
SE. 

W. 
NW. 
SE. 
SE. 
SE. 

N. 
NW. 


Miles 
per 
hour. 
10 


Fair 


do 

Fair 


7 


29 


Cloudy 

Fair 


17 


30 


Cloudy 

Clear 


13 


May 1 
2 


do 

Cloudy 


10 


Fair 


24 


3 


do 


35 


4 


do 

Cloudy 

do . , 


Clear 


33 


5 


Fair 


32 


6 


do 


29 


7 


...do 


Clear 


41 


8 


Fair 


do 


36 


9 




do 

Cloudy 

do 

do 


16 


10 
11 
12 
13 


do 

do 

do 

Fair 


28 
22 
11 
24 


14 


Clear 













INFLUENCE OF TEMPERATURE ON DIFFUSION. 

Directly and indirectly, temperature is responsible for the destruc- 
tive abundance of Toxoptera graminum in the United States. Di- 
rectly, because the species will breed throughout the winter months 
at a temperature under which its natural enemies will remain inac- 
tive, and besides, it is probably due to this influence that the sexual 
forms and eggs occur, so far as known, only over the northern por- 
tion of its range. Our extended investigations have led to the sus- 
picion that, but for the viviparous reproduction in such overwhelm- 
ing numbers in the South, during winter end early spring, to drift 
northward with the season, there would be little if any damage caused 
by its occurrence in the Northern States, where in fairly severe win- 
ters it probably winters over in the egg stage only. For this 
reason the authors have thought investigations of the egg and its 
development of decided economic as well as scientific importance, 
and the junior author has therefore made a brief study of the em- 
bryology of the species. 

The temperatures prevailing over the country where Toxoptera 
has worked its most serious ravages, and departures from the normal 
during the season of greatest activity are all given on the tempera- 
ture diagrams, Nos. I to V (pp. 15, 21, 25, 26, 28) . The upper numbers 
indicate the normal temperature, the lower the departure therefrom 
( f ' + " meaning above and tl — " below). Each separate page relates 
to one of each of the five consecutive outbreaks. From these it will 
be seen that outbreaks of Toxoptera have succeeded only winters with 



INFLUENCE OF TEMPERATURE ON DIFFUSION. 89 

the temperature in the South above the normal, followed by springs 
during which the temperature was below the normal. The tem- 
perature during December, 1902, was below the normal in the South- 
west. (See Diagram II.) In January, 1903, it was above, but 
below again in February, and about normal or above in March and 
April, . the result being that only incipient outbreaks occurred in 
northern Te^as and probably South Carolina. (See Diagram II; 
fig. 5, p. 20.) If the series of temperature maps (Diagrams I-V) 
be compared with those showing the area covered by each invasion 
the relation between abnormal temperatures and these invasions 
will be clearly apparent. 

These records are those of the United States Weather Bureau and 
are therefore correct so far as general field temperatures are involved. 
When it comes to a consideration of the exact effects of temperature 
and humidity upon the individual Toxoptera, however, the figures 
will not apply with mathematical exactness, for the reason that to 
secure this information it is necessary to learn the exact conditions 
in the midst of the insects themselves at the exact time that such 
data are being secured. To illustrate, the instruments of the 
Weather Bureau kept in the shade may indicate a certain tempera- 
ture, yet in a field perhaps a mile distant on a sunny day, and down 
among the plants in the midst of the developing insects, there may 
be several degrees difference in temperature. As will be noted 
farther on, Mr. Luginbill has found this difference to amount in some 
cases to several degrees. Besides, it is easy to conceive of other 
conditions which might have precisely the reverse effect. Further- 
more, there mil be a difference in temperature as between fields with 
a sandy and a cla} r soil or between a southern and a northern expo- 
sure, or with a soil dry on the surface as against a soil with a wet sur- 
face. It will be observed, therefore, that while the exact tem- 
perature at which Toxoptera will reproduce, viviparously, is of 
scientific interest, such information is of minor significance in the 
field, where it is the more generally prevailing weather conditions, 
such as are secured by the United States Weather Bureau, over wide 
areas that become of greatest importance, Mr. II . A. Vickery, on 
December 4, 1908, at Richmond, Ind., with 5 viviparous females 
under observation, found that young were produced sparingly at a 
temperature of 40° F. This was indoors, in a room slightly heated by 
an oil stove so that the temperature was under control, and frequent 
readings were made during the day. Under the same conditions 
numerous young were produced when the temperature reached 45° 
to 53° F. " 



90 

Tabulated, the results of Mr. Vickery's rearings are as follows: 

Table IX. — Experiments with 5 viviparous females of Toxoptera graminum to determine 
minimum temperature at which reproduction will take place. Richmond, Ind., 
December, 1908. 



Date. 


Temperature. 


Number 
of young 
produced. 


Minimum. 


Maximum. 


Dec. 3 
4 
5 

6 
7 
8 
9 


°F. 
40 
40 
40 
40 
26 
35 
39 


°F. 
45 
41 
53 
45 
49 
50 
50 




1 
6 


1 
7 




After December 9 the outside temperature increased so that con- 
trol indoors was not possible. 

At Dallas, Tex., January 3 to 14, out of doors and under natural 
conditions, with thermometer within a few feet of the five female 
Toxoptera 1 to 3 days after maturity, Mr. Urbahns found that 
young were produced as follows: 

Table X. — Experiments with 5 viviparous females of Toxoptera graminum to determine 
minimum temperature at which reproduction will take place. Dallas, Tex., January, 
1908. 





Temperature. 




Date. 




Number of young produced by 






each individual. 




Minimum. 


Maximum. 






°F. 


°F. 












Total. 


Jan. 3 


47 


68 


1 


1 


1 


1 


1 


5 


4 


55 


78 


3 


3 


1 


5 


4 


16 


5 


37 


69 


3 


3 


1 


2 


2 


11 


6 


22 


42 




















7 


21 


32 

















o 


8 


29 


45 

















o 


9 


44 


74 


4 


2 





3 


4 


13 


10 


37 


74 


4 


4 


(M 


3 


5 


16 


11 


14 


15 



















12 


10 


22 



















13 


21 


32 



















14 
Total.. 


32 


71 



15 


















13 


3 


14 


1G i 




1 







i Died. 



INFLUENCE OF TEMPERATURE OX DIFFUSION. 



91 



Further observations made by Mr. Urbahns on these same dales 
with eight additional females, the offspring of which were not counted, 
are of much interest and are given herewith. 

January 3. Two reproducing. 
January 4. Four reproducing, 1 pupating. 
January 5. Five reproducing. 
January 6. All torpid, seemingly frozen. 
January 7. All torpid, seemingly frozen. 
January 8. All torpid, none reproducing. 
January 9. Seven reproducing, 1 still pupa. 
January 10. Seven reproducing, 1 still pupa. 
January 11. All torpid, seemingly frozen. 
January 12. All torpid, seemingly frozen. 
January 13. All torpid, seemingly frozen. 

January 14. Adults and young fallen from the plants and lying on the ground. 
All except 3 inactive. 

One female of the first five died on the 10th and nearly all of the 
others survived but a few days; only one was alive on the 20th. 

During the spring of 1908 the junior author was engaged in an 
extensive series of rearing experiments at Richmond, Ind. Both 
plants and insects were kept out of doors in a small rearing house 
(see PL II, fig. 1), with a thermograph placed in their midst, so that 
exact temperature changes were continuously recorded. Plants 
were grown in flowerpots and over them in each case was placed a 
lantern globe with the top covered with cheesecloth. Whatever 
the effect of this inclosure and cover might have been it was evi- 
dently uniform and, therefore, affected all of the viviparous female 
Toxoptera on these plants to the same degree. 

Taking five viviparous females, each a stem mother, colonized 
separately on single plants, in a precisely similar inclosure, and keep- 
ing a record of the number and date of young born, we have the fol- 
lowing tabulated results: 

Table XI. — Effect of temperature on reproduction of Toxoptera graminum, Richmond, 

Ind., 1908. 



1 


Tempera- 












Tempera- 










ture. 












ture. 








Dite. 




Number you 
duoed by 


ng pro- 


To- 
tal 


Date. 




Number young pro- 


To- 
tal 




















Mini- 


Maxi- 


dividual. 






No. 




Mini- 


Maxi- 


dividual. 




i\0. 




mum. 


mum. 












mum. 


mum. 










°F. 


°F. 
















°F. 


°F. 














Apr. 18... 


55 


63 


2 




2 





2 


6 


May 1 


29 


56 




















19... 


50 


70 


4 


2 


2 


1 


2 


11 


2 


35 


47 





2 


1 





C 


3 


20... 


39 


68 


2 


2 


2 








6 


3 


37 


55 


1 


2 


2 


1 





6 


21... 


33 


08 


2 


2 


2 


1 





7 


4 


41 


50 




















22... 


35 


74 


2 




1 


1 


1 


6 


5 


49 


52 














1 


1 


23... 


52 


79 


2 


5 


5 


1 


1 


14 





49 


70 


1 


2 


2 








5 


24... 


00 


71 


3 


3 


4 





1 


11 


7 


41 


63 





0. 


1 








1 


25... 


01 


74 


3 


4 


ft 


1 


2 


15 


8 


41 


49 


1 














1 


26... 


53 


80 


3 


5 


3 


3 





14 

























27... 


42 

38 


67 
54 



2 


I 


2 



3 




1 



8 
2 


Total 
Total prog 




29 


33 


36 


15 


12 




28... 


eny during 




29... 


36 

33 


46 
47 


1 







2 



3 



1 



7 



life 




60 


47 


69 


39 


29 




30... 







92 THE SPRING GRAIN- APHIS OR 






Of the five individuals involved in Table XI the two last hatched 
from the egg March 24, the other three on March 27. This table 
indicates the influence of high temperatures on reproduction, but 
also shows that these affect the individual female to varying degrees. 
The totals for the life of individual females show that all of these 
were in the vigor of life, not having reached the decline at the time 
the observations were made. 

These tabulations are taken from records of regular rearing and 
reproduction investigations, and were selected wherever there 
occurred a number of consecutive days with temperatures varying 
both above and below freezing during each 24 hours. 

By referring to the continuous rearing by the junior author it 
will be observed that with favorable conditions a female Toxoptera 
will produce young every day during the most vigorous portion of 
her life, the exceptions being toward the close thereof. 

It would probably be well to mention in this connection some 
observations of the junior author in regard to the amount of cold 
that can be endured by Toxoptera. • 

On November 13, 1908, several viviparous females that had been 
producing young were frozen solidly in a block of ice. They were 
thawed out after 8 and 24 hours, respectively, and all died. These 
may have been somewhat weakened by age, however, so on the 14th 
2 oviparous females, 1 winged viviparous female, 1 adult viviparous, 
and 2 individuals that had cast the third molt were frozen in a block 
of ice and allowed to remain so for 24 hours. About an hour after 
being thawed out, at a temperature of about 45° F., 1 oviparous 
female and the winged female turned dark and died, the others keep- 
ing color, but showing little signs of life. About 3 hours after 
there were signs of life among the remaining ones; 7 hours after 
thawing out they were still feeble; 24 hours after thawing out the 
temperature was raised to 60° F and 1 molted. On the third day 
after being thawed out there were 2 young in the cage. Six days 
later all were dead except the one that was giving birth to young, 
and her progeny. This will give some idea of the tenacious grip 
Toxoptera has on life. 

Attention may properly be called to the fact that unless the utmost 
caution is employed in the examination of plants for newly-born 
young there is great likelihood that some of them may be overlooked. 
Thus they may be born one day under a high temperature but remain 
undiscovered until later, when the temperature is much lower, and of 
course be credited to the later date. In the light of all of the observa- 
tions made by those engaged in these investigations, the minimum 
temperature under which reproduction begins is about 40° F. Pos- 
sibly reproduction may occur under some obscure favorable circum- 



INFLUENCE OF TEMPERATURE ON DIFFUSION. 93 

stances at a slightly lower temperature, but these instances are 
probably too infrequent to become of economic importance. 

With the eggs in the North the case may be more important, because 
these, deposited in dead leaves of bluegrass, and sometimes probably 
buried under several inches of this matted grass, with the living leaves 
covering this over, the temperature and moisture would both be 
greater than at several feet above ground without such protection. 
Mr. Philip Luginbill of this bureau in April, 1911, proved this to be 
true. He placed a thermometer in just such a position as men- 
tioned above, in a protected nook where the sun could shine directly 
on it in the grass and no wind could reach it and found that the 
temperature was 10° to 12° F. higher than when the thermometer 
was several feet above the ground and in the shade. The junior 
author has found that eggs are deposited in just such places, and that 
hatching takes place in spring at a temperature ranging, as recorded 
by the thermograph, from 32° to 62° F. It would appear that 
eggs deposited in a position as mentioned above would hatch sooner 
than those deposited in places where the temperature would not be 
so high and the stem mothers from the former would reproduce, 
the pest becoming more abundant in the spring and making its way 
from grass to grain earlier and in greater numbers than they would 
from the cooler locations. 

This leads us to a very interesting and important point in tem- 
perature effects on the species. In the South, seemingly south of about 
latitude 35° to 36° north, it has been impossible to find eggs of this 
and other species of aphidids in the fields. There is in the perpetua- 
tion of the species no apparent need of this stage, however, as it is 
able to continue throughout the entire year reproducing viviparously. 
In the North this is probably not possible except during very mild 
winters. The situation is therefore about like this: Gradually as 
we proceed southward from about latitude 38° the sexual forms and 
eggs disappear, while to the north of about latitude 36° hibernation 
is confined more and more to the egg stage, until this becomes ex- 
clusively the state in which the winter is passed. 

The practical, economic importance of this is that there is con- 
siderable doubt relative to the amount of injury the pest would 
cause north of this belt of country if there were no Toxoptera drifting 
in from the south. In other words, but for the countless myriads 
developing south of this belt and sweeping over and beyond it, there 
would be few if any destructive ravages. If this is the true state 
of affairs, the oats crop north of this belt is to a certain degree de- 
pendent upon the success or failure in controlling the pest in Texas, 
Oklahoma, New Mexico, and South Carolina. 

Summarizing, then, it would appear from the information we have 
been able to obtain, and which is given throughout this publication. 



94 THE SPEING GKAIN-APH1S OR 

together with that contained in the various tables and diagrams 
relating to temperature effects upon this insect: (1) That mild 
winters are of much more vital importance in Texas than they are 
in the latitude of southern Kansas and northward, and (2) that the 
influences of abnormally warm weather, if the temperature rises high 
enough, have the effect of bringing about activity among the parasites, 
which has a restraining effect upon the increase of Toxoptera. 

In the North, where the pest winters over wholly or largely in the 
egg stage, warm winters are of less importance, while abnormally 
cool weather during spring and early summer exerts a far greater influ- 
ence. This fact renders a study of the embryology and temperature 
effects upon eggs and stem mothers necessary to a full understanding 
of the entire problem, extending as it does over both North and 
South. 

The fact just stated is somewhat peculiar and was unexpectedly 
revealed by the combined- studies of those engaged in the investiga- 
tion of the insect, and called for a study of the development of the egg, 
which has been carried on by the junior author with the results 
given in the following pages. The most important influence of 
temperature is, of course, upon the development of its principal 
natural enemy, ApJiidius testaceipes, further discussed in connection 
with the studies of that insect. 

EMBRYOLOGY. 

Although the development of the parthenogenetic egg in Aphididge 
has received considerable attention from several authors, that of the 
true egg has received very little study. Hence the junior author 
has given a limited amount of time to the study of certain important 
phases in the development of the winter egg, as contrasted with the 
winter condition of the viviparous insect in the South. 

Not wishing to duplicate the work of the other writers, who have 
confined their studies for the most part to the earlier stages of develop- 
ment, he has begun with the formation of the blastoderm, his main 
object being to follow the principal stages of development of the 
embryo through the fall until growth is checked by freezing tempera- 
tures, to note the time when growth is resumed in spring, and to 
observe the effect of varying temperatures on development, all of 
which has to do with the fluctuations of the insect in point of numbers 
in the North and relates to its economic importance, besides balancing 
our knowledge of the insect at a corresponding season in the South. 

Most of these studies were carried out at the University of Illinois 
under the supervision of Dr. J. W. Folsom. We are deeply indebted 
both to him and to Dr. W. M. Wheeler of Harvard University for 
their kindly criticisms and helpful suggestions. 



EMBRYOLOGY. 95 

METHODS AND MATERIAL. 

The material used in this investigation was collected in the autumn 
of 1908 at Richmond, Ind., and in 1909 and 1910 at La Fayette, Ind. 
The eggs were killed and fixed mainly in two solutions that are practi- 
cally the same. The first was a saturated solution of bichlorid of 
mercury (corrosive sublimate) in 35 per cent alcohol, 95 volumes, 
and glacial acetic acid, 5 volumes. The second was a saturated 
solution of bichlorid of mercury in 50 per cent alcohol, 94 volumes, 
and glacial acetic acid, 6 volumes. The fixing fluid was raised to a 
temperature of 75° to 80° C, poured over the living specimens, and 
allowed to act from 5 to 10 minutes, after which it was replaced by 
the same solution, cold, for an equal length of time. The specimens 
were then washed in 70 per cent alcohol, in which they were kept 
until sectioned. Gibson's fluid was found to be a very good killing 
and fixing agent also. 

For sectioning, the following method was employed: The eggs 
were punctured with a fine needle, dehydrated, and kept 20 to 
30 minutes in paraffin of about 54° C. melting point. They were 
oriented in a watch glass (that had previously been smeared with 
glycerin) with a hot needle, under a binocular microscope, the bottom 
of the watch glass being first quickly cooled with a little cold water. 

The eggs were cut with a Minot-Zimmermann microtome in 
sections from 8 to 13 /* in thickness, attached to the slide with Mayer's 
albumen fixative, and stained with Delafield's hematoxylin or by 
Heidenhain's iron-alum-hsematoxylin method. 

Surface views of the embryo were obtained by dissection. For 
dissections it was found that the best results were obtained by using 
material that had been freshly fixed and washed. Grenadier's 
alcoholic borax-carmine was used for staining in toto. 

GENERAL DESCRIPTION OF THE EGG. 

The eggs are broadly elliptical with a slight reniform tendency. 
They are 0.70 to 0.78 mm. in length and 0.33 to 0.45 mm. broad. 

At oviposition the egg is a very pale yellow, changing in a few 
hours, at a temperature of 50° to 70° F., to a faint greenish color. At 
this stage there appears an almost circular area of darker green at one 
pole of the egg; we have termed this the "ovarian yolk," a brief 
description of which occurs in the following pages. At the end of 24 
hours the walls of the egg about the ovarian yolk appear denser 
and of a deeper green. The germ band is now forming and invaginat- 
ing. During the next 24 hours this process is completed, the egg 
becoming a darker green in the meantime. By the third day a rod- 
shaped body can be seen near the center of the egg. This object is 
the submerged germ band. By the end of the third day the egg 
becomes black. 



96 

All these changes can be readily observed with a hand lens by 
holding the egg up to the light. At low temperatures (below 40° F.) 
these changes take place slowly, 10 or more days being required 
for the egg to turn black, if the temperature is near the freezing 
point. The black coloration is apparently due to a pigment in the 
shell; the green color, to the developing embryo. 

At deposition the egg is coated with a viscous substance which 
hardens in a few days, fixing the egg firmly to the object upon which 
it rests. 

There are but two membranous coverings to the ripe egg, the 
chorion, or shell covering, and the vitelline membrane. 

The chorion is a rather tough, leathery, homogenous membrane 
which under a hand lens appears smooth and shining. With a com- 
pound microscope very faint lines or cracks can be sometimes ob- 
served on the surface, although usually the surface appears perfectly 
smooth, with no markings whatever. 

The vitelline membrane is structureless, colorless, and trans- 
parent. Under the vitelline membrane is the peripheral layer of 
protoplasm. This layer is very thin and very finely reticular. It is 
continuous over the surface of the egg, the cleavage cells lodging in 
it to form the blastoderm. 

Internally the egg consists chiefly of a compact mass of yolk 
granules, supported within the meshes of almost clear protoplasm. 
The yolk granules are structureless and subspherical in shape and 
vary greatly in size, ranging from 0.0027 mm. to 0.013 mm. in 
diameter. 

At the posterior pole of the egg is a large, dense, almost spherical, 
granular mass. These granules are 0.0019 mm. in diameter, are 
almost uniform in size, and the central area apparently takes the stain 
slightly as though it were a chromatinlike substance. As previously 
stated, we have termed this mass the ovarian yolk. It is evidently 
not homologous to the secondary yolk of the parthenogenetic em- 
bryos. The ovarian yolk is formed approximately at the same time 
as the formation of the main yolk mass of the egg, while in the case 
of the parthenogenetic forms of aphidids the secondary yolk enters 
the egg as the blastoderm is forming. It appears also, from our 
material, that this ovarian yolk is not exactly homologous to the 
"pole disk ,; described and observed by Hegner (1908), as we have not 
been able to observe that it affects the nuclei in any way, nor have 
we found any cells which we think correspond to his "pole cells." 
The function of this granular mass seems to be the nourishment of 
the developing ovaries, and we have therefore called it ovarian yolk. 
It is not entirely used up in the early stages of embryonic growth, 
and remains in close proximity to the developing ovaries throughout 
the later stages. 



EMBRYOLOGY. 97 

Tannreuther (1907, pp. 631, 632) states that in the species he 
studied some of the follicular nuclei of the wall of the oviduct which 
enter the posterior pole of the egg divide several times, the chromatin 
breaking up into smaller parts and becoming vesicular. These small 
vesicles then usually unite and form a common spherical mass, 
though in some cases thev remain isolated. 

In Toxoptera graminum we find no trace of true nuclei within the 
ovarian yolk (the homologue of Tannreuther's secondary york of the 
winter egg) until the blastoderm is formed, at which time cells may 
be found that are apparently migrants from the primary yolk. 

OBSERVATIONS. 

For convenience of reference 9 consecutive stages of development 
are here designated, as follows : 

Stage 1 (PL III, fig. 1). — Blastoderm just forming, only part of 
the surface being covered by the cleavage cells. 

Stage 2 (PL III, figs. 2-4). — This shows early and later stages of 
invagination of the germ band. The position of the ovarian yolk in 
relation to the invaginating germ band is shown here. 

Stage 3 (PL IT, fig. 1). — The germ band is still adhering to the 
posterior pole of the egg. 

Stage 4 (PL IV, figs. 2, 3). — The germ band is entirely submerged 
in the yolk, is tubular in form, and uniform in thickness. 

Stage o (PL IV, fig. 4). — During the fifth stage the germ band has 
differentiated into the amnion and the germ band proper. 

Stage 6 (PL V, fig. 1). — The germ band shows differentiation into 
layers, and the fundaments of the segments are evident. 

Stage 7 (PL V, fig. 2; PL VI, fig. 1).— The fundaments of the ap- 
pendages have appeared and the invaginations for the stomodseum 
and the salivary glands are evident. 

Stage 8 (PL V, fig. 3; PL VI, fig. 2).— The appendages are much 
longer, and the invaginations for the stomodaeum and proctodeum 
are well advanced. The latter is not indicated in Plate V, figure 3, 
as the last segment curves backward too far. 

Stage 9 (PL VII, figs. 1, 2, 3, 4).— The illustration of this stage is 
intended mainly to show the manner in which the embryo reaches 
the surface and the position of the dorsal organ. 

In Stage 1 (PL III, fig. 1) the blastoderm is beginning to form. As 
the cleavage cells become more numerous within the yolk-mass some 
of them migrate to the surface and lodge within the peripheral layer 
of protoplasm, where, according to Tannreuther (1907), they divide 
again, the protoplasm of the nuclei merging with that of the periph- 
eral layer. The formation of the blastoderm takes place more rapidly 
in the region of the anterior pole, the posterior being the last covered; 
26675°— Bull. 110—12 7 



98 

the entire layer is then one cell in thickness. The blastoderm, how- 
ever, does not cover the surface of the ovarian yolk. 

Not all of these cleavage cells reach the surface; many remain 
behind, increasing in number within the yolk. These latter cells are 
indistinguishable from those of the blastoderm. Figs, la and lb 
represent two of these cells magnified 845 diameters, showing them 
to be star-shaped masses of protoplasm with a large oval coarsely 
granular nucleus, more often with a large clear area of nuclear sub- 
stance around the mass of chromatin granules. 

At the posterior pole, about the ovarian yolk, the blastoderm be- 
gins to thicken and to invaginate (Stage 2, PL III, figs. 2-4). This 
is the beginning of the germ band. At this stage {Stage 2) some of 
the yolk cells apparently pass into the ovarian yolk. Tannreuther 
(1907, p. 631) states that the thickening of the blastoderm is caused 
by the rapid division of the blastoderm cells of this particular part. 
We find, in addition, that some of the cells from the interior of the 
egg migrate to the posterior pole to assist in this process. Each of 
the cells of this thickened area is very elongate, and, from a surface 
view, now has a somewhat polygonal shape, with a large coarsely 
granular nucleus. The growth of the cells of the germ band carries 
the ovarian yolk toward the center of the egg (see PI. Ill, fig. 4). 
The part of the blastoderm that invaginates first becomes the posterior 
part of the embryo, and that part that invaginates last becomes the 
anterior portion. 

In Stage 3 (PL IV, fig. 1) the germ band is ready to free itself from 
the blastoderm. The former is now cone-shaped, the base being 
closed by the ovarian yolk. 

When the germ band releases itself from the blastoderm, it leaves 
behind what we have termed the "polar organ :" A cluster of cells 
embedded within a mass of protoplasm. These cells soon group 
themselves into a more or less spherical mass, with a less dense 
vacuolar area at the center (see PL IV, ^g. 4). In later stages this 
central area appears denser and structureless, as though filled with 
a fluid, and is of a yellow color, not taking the stain, and opening 
directly upon the surface of the egg. For these reasons we suggest 
that it may be an organ of excretion. When development ceases in 
the fall, this body is still present. 

What was formerly the blastoderm now becomes the serosa. The 
cells are much more widely spaced now and this wall is much thinner, 
except at the anterior pole, where the cells are apparently crowded 
more closely than before. Some of these cells often show large 
vacuoles on the side toward the yolk. 

At Stage 4 (PL IV, Hg. 2) the germ band is completely submerged 
in the yolk, has assumed a tubular shape, and is near the center of 
the egg. The walls are of uniform thickness and composed of a com- 



EMBRYOLOGY. 99 

pact mass several cells thick, some of which are vacuolated, and 
having a coarsely granular nucleus. Figure 3 of Plate IV shows a 
cross section — slightly oblique, however — of the germ band. 

The yolk granules of the primary yolk are now more numerous 
near the embiyo. 

In Stage 5 (PL IV, fig. 4) the germ band has clearly differentiated 
into the amnion and the embryo proper; these gradually merge into 
each other. Tins differentiation apparently takes place by a gradual 
migration of cells to one side of the germ band. The cells of the 
amnion at this time resemble very closely those of the germ band 
proper. The germ band begins to fold in this stage and its anterior 
extremity begins to broaden and flatten. The ovarian yolk has de- 
creased in volume and has assumed a more anterior position in rela- 
tion to the embryo. The yolk cells in both the primary and ovarian 
yolk have lost somewhat their amoeboid character, and now consist, 
each, of a large granular nucleus, with a much thinner area of pro- 
toplasm about it. The primary yolk granules are smaller and much 
less numerous than before and are collecting in masses about the 
yolk cells, with indications here and there of a partition, or wall, 
forming between them. This stage is reached by the end of the second 
day, under favorable weather conditions. 

The "polar organ" and protoplasm at the posterior pole contain a 
large central vacuolar area now. 

In Stage 6 (PI. V, fig. 1) the germ band has greatly increased in 
length, is folded upon itself, and almost forms a loop, the anterior 
and posterior extremities nearly touching, and both pointing to the 
posterior pole. A portion of the posterior extremity of the germ band 
is again folded upon itself. It is now differentiated into three layers, 
winch we take to be, respectively, ectoderm, mesoderm, and ento- 
derm. The ectoderm and mesoderm consist of a compact mass of 
columnar cells, two cells thick. The entoderm is much thinner and 
less compact and forms an almost continuous sheet over the inner sur- 
face of the germ band. Its cells resemble yolk cells very closely. 

In this stage fundaments of the bocly segments appear as slight 
elevations of the ectodermal surface. The ovarian yolk has assumed 
a more anterior position in relation to the embiyo than in the pre- 
ceding stage. Between the ovarian yolk mass and the germ band is a 
group of cells that have apparently separated off from the mesoderm. 
From this group of cells, in later stages, the generative organs arise. 
The amnion now covers the ventral surface of the embryo and the 
other surface of the embryo is in contact with the yolk. The amnion 
is a very thin, delicate membrane, its cells being widely spaced and 
quite small. The intervening protoplasm between the cells of the 
serosa has become more constricted and the cells have taken more of 
an elongated oval shape. The primary yolk has now become defi- 



100 



nitely segmented into more or less spherical masses, separated by 
thin walls, each area or mass containing a number of yolk granules 
and from one to several cells. The polar organ is now almost spher- 
ical, with a central, pear-shaped area of dense, structureless, non- 
staining matter of a yellowish color, and an anterior opening. Al- 
though this evidence is insufficient it possibly indicates that the func- 
tion of this organ is excretory. The embryo reaches this stage of 
development about the third day, under favorable conditions of 
temperature. 

In Stage 7 (PI. VI, fig. 1) the embryo has changed its position so 
that from a side view it has the form of a reversed figure 6. The 
portion that in the preceding stage was folded upon itself ventrally 
has reversed its position and folded back dorsally. The ovarian 
yolk is now in the region of the first abdominal segments. It is in 
contact with the embryo, and the group of cells that separated it 
from the embryo in the preceding stage has assumed almost a spheri- 
cal form, and a more posterior position, forming the genital organs 
later on. 

The three primary regions, cephalic, thoracic, and abdominal, are 
now sharply marked. Each region is distinctly segmented. The 
cephalic region has 5 segments indicated, the thoracic 3, and the 
abdominal 9, the last abdominal being relatively quite large. There 
are now 15 conical appendages. The antennae arise from the pos- 
terior margin of each cephalic lobe. The labrum is between and slight- 
ly anterior to the antennae. The mandibles are nearer the median 
plane than the fundaments of the maxillae and the labium. The next 
three pairs of appendages represent the first, second, and third pairs 
of legs. Plate V, figure 2, represents a surface view of stage 7, show- 
ing the embryo straightened out and the position of the appendages. 
All of these appendages are evaginations of the ectoderm, cross-sec- 
tions showing an external layer of ectoderm cells and an inner layer 
of mesoderm cells. 

The stomodaeum (PI. VI, fig. 1) appears now as a simple invagina- 
tion of the ectoderm, the posterior wall of the labrum forming its 
anterior wall. The proctodeum has not yet appeared, The salivary 
glands (PL VI, fig. 1) are represented by a deep, bilobed, ectodermal 
invagination between the cephalic and thoracic regions. There is 
now a star-shaped mass of protoplasm about the nucleus of the 
ovarian yolk cells and the yolk granules are grouped around these 
cells. 

The primary yolk is grouped very much as in the preceding stage 
with the exception that the masses are smaller and do not contain as 
many nuclei. 

The polar organ is smaller than formerly, with a smaller number 
of cells. It still contains a yellowish mass and communicates with 
the outer surface of the egg. 




3a 



Jb" I 






Fiq.e 




' °o o °0°° Q < 




Development of the Embryo in the Egg of Toxoptera graminum 



Fig. I- Lolled i a limit seel iii! i show in- the M:ist in In in narth I'm me. I , I n'iiiu Ilii I lies! advanced ill I lie anterior ivnrai. I In' i.e. a; ol n\ a. la 11 Mill, i ; Indeed a I Ilia fain mr 
pole. Figures In ami II) represent I he \ 1. Ik rail.-, im.il; ni I ie.1 s-lf. . I iai art crs. Fiji. _'.— Lungil rid inal section showine. t he I hickening of Ilia I. last o. term alioiil the in arian yolk 

previous in in vaginal inn. Magnilied i.'.li diameters. Fill. :i. - Longitudinal section 1 cpiescnl 11 i.u Hie mini I .ami al I lie In-ginning of in\ aginal ion, folding inward I 

the ovarian volk. Magnified l.'.h diameters. I- ie. 3«.— seat ion of the blastoderm. Ma quilled Jill diameters. Fin. 4.— Longitudinal seat inn ol a more ad vanned stage of 
invagination, the germ hand having almost closed over the ovarian volk. Magnified l.'.tj diameters. (Original.) 



i of Entomology, U. S. Dept of Agriculture. 





OZj. 



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\ °S§&£ 'ML am $£$&■ 



FiQ.6 




fi* Fiq.4. 



Development of the Embryo in the Egg of Toxoptera Graminum. 

Fig. 1.— Longitudinal section representing the somewhat cone-shaped germ band ready to release itself from the surface of the 

egg, the ovarian voile dosing the posterior exireinilv. Magnified l.'.ii diameters. Fig.-J.-SagiH.il scetion representing I »' 
tubular germ ban. I completely subnieigea within the volk, the anterior extremity being continuous v, it h the sides and tlie 
I'ostenoi end closed by the ovarian volk. The "polar organ" is represented by a mass of cells and protopla m at i he pos- 
terior pole. Magnified llti diameters. Fig. 3. — 'I lansveisc isoinewhai oblique) section of the germ band. .Magnified l.,i> 
diameters. Fig. 4.— Sagittal section slewing i lie genu band folding and differentia I ing into anon..,, aid tiiii hand proper 
the ovarian yolk has taken a more anlerim position, the '-polar organ" U vacuolated now. Magnified l.jf> diameters. 




Fiq. \ 




Fio.2. 



Fiq.3. 



Development of the Embryo in the Egg of Toxoptera graminum. 



Fig. 1.— Sagittal section showing Ihe genu band differentiated into three layers and folded almost upon itself, (he ovarian yolk beings 
later becomes an ovary. The " polar organ" is now more nearly circular. Magnified l.'iii diameters. Fig. 1'.— .Surface view of Plate ' 
Fig. 3.— Smlacc view ol Plate VI, figure i>. Magnified l.M. diameters. (Original.) 



, figure 1. Magnified 156 diameters. 



ab.P. 





Development of the Embryo in the Eqg of Toxoptera gram 



Fig. 1.— Sagittal seel ion of the einluvo showing i lie segmentation. 'Die invaciuai ion "I lliesalivai v -Ian, Is is now e\ ideal , The 1'undumonis of I In' ovai ies have assumed more 
definite shape and liaveslnl'led in position. 'J lie ovaiian volk is greallv changed in appeal anoe and has la ken up a posh ion at I he anterior pon ion ol' I lie alidominal region. 
The "polar organ" now shows a huge, somew ha I pear-shaped eenlriil cavil y which opens upon l he sin luce ol I he egg and is Idled wil h a > el low is h sol ,siance. .Magnified i;,i; 
diameters. Fig. L\— Sagitlal seel ion (sliglillv olilhpiei showing o much more advanced si age ol erou I h I hail 1 lial ol he tire 1 , 1 he abdominal region lining reversed its posi- 
tion bv Pending around Puck ward and inclosing ihe ovarian yolk. The inesenl eion is in process ol'lormatioii. The ovarian yolk is granular and ils cells are I. leaking down. 
The "polar organ " is much the same as in the preceding stage. Magnified l"i; diameters. (Original.) 



EMBRYOLOGY. 101 

In Stage 8 (PL VI, fig. 2) the posterior or abdominal region of the 
embryo has now completely changed its position, having folded back 
dorsally about the ovarian yolk. Plate VI, figure 2, shows a sagittal 
(slightly oblique) section of an embryo at this stage. There are ap- 
parently only 9 abdominal segments. Both the stomodseum and the 
proctodeum are plainly in evidence now, and the mesenteron is in 
course of formation. The latter is formed above and rests upon the 
ovarian yolk. This yolk now has a granular appearance, and the yolk 
cells within it appear to be breaking down. It is still divided off into 
subspherical masses. The polar organ is smaller than in the pre- 
ceding stage and the pear-shaped area in the center is filled with a 
yellowish substance as before. The ovaries are represented in this 
section by a circular mass of cells above the ovarian yolk. The pri- 
mary yolk is grouped and divided off by protoplasmic threads, very 
much as in the preceding stage, but is not quite so abundant now. 
Plate V, figure 3, shows a surface view of the embryo, straightened 
out to its full length. It mil be seen that the appendages are now 
much more elongate, the thoracic appendages showing traces of 
segmentation. All the appendages are now directed posteriorly 
and lie flat upon the body. 

This is the stage in which the majority of the embryos pass the 
winter. It is very doubtful if any of the stages earlier than the 
seventh are able to survive the winter. Instances have come under 
our observation in which embryos in the sixth stage have been killed 
by very low temperatures. When heavy freezes do not occur until 
sometime in December, a very large percentage of the eggs hatches; 
on the other hand, however, when heavy freezes begin in November, 
large numbers of the eggs are killed in the early stages, since large 
numbers of the eggs are deposited in this month. An early autumn, 
therefore, followed by a severe winter, would limit to a great extent the 
number of stem mothers of the following spring. 

Stage 9 (PL VII, figs. 1-4) represents the stages of growth occur- 
ring in the latter part of February and the first" of March. When 
the embryo is ready to come to the surface of the egg (PL VII, 
fig. 1), it moves forward in the yolk until the cephalic lobes come 
into contact with the polar organ. It will be observed that there 
is quite a gap between figures 1 and 2, and at present we have no 
material from which this missing link can be supplied. Figure 2 
shows the dorsal organ already formed. As we have no intermediate 
stages we can not state definitely whether this is the true dorsal 
organ or the dorsal and polar organ combined. It is probably the 
latter, as we do not find any traces of the polar organ at any other 
point in the embryo. It is very probable that the surplus cells of 
the serosa, at the time the embryo comes to the surface of the egg } 
collect at and group themselves about the polar organ, as there 



102 

appear to be a greater number of cells about this body at this time. 
There is no trace of the dense yellowish center of the polar organ, 
otherwise it resembles this body very closely. However, as we have 
lost track of this organ in the gap between figures 1 and 2, and on 
account of the close resemblance between it and the dorsal organ 
of other insects, we have designated it as the latter. At a later 
stage (PL VII, fig. 3) the dorsal organ has assumed a more nearly 
circular shape, the mouth having almost closed, inclosing a some- 
what pear-shaped space. At a still later stage (fig. 4) the dorsal 
organ has released itself from the margin, migrated backward, and 
begun to disintegrate. At length it disappears by absorption in 
the body cavity. 

At first we were not able to note a revolution of the embryo, but 
later studies show that such a revolution does occur between figures 
1 and 2 of Plate VII. 

After the ninth stage the development goes t>n very rapidly, and 
by the latter part of March the eggs are ready to hatch. 

During the fall of 1909 a number of eggs were collected that had 
been deposited in October and November, and these were kept until 
the spring of 1910 to note the time of hatching. No heavy freezes 
occurred until the 3d of December. It was found that although 
there was nearly a month's difference in dates of deposition there was 
not more than four or Hve days' difference in the time of hatching. 
An average of 64 per cent of the eggs hatched. We have also learned 
that eggs will not hatch unless subjected to freezing temperatures. 

SUMMARY OF EMBRYOLOGICAL DEVELOPMENT. 

There is a large almost circular mass of ovarian yolk at the poste- 
rior pole of the egg. 

Development begins almost immediately after oviposition, and 
proceeds more rapidly in the region of the anterior pole until after 
the blastoderm forms, after which growth almost ceases in this region. 

The blastoderm originates through the migration of yolk cells 
from the interior to the surface of the egg. All of the yolk cells, 
however, do not take part in the formation of the blastoderm, part 
remaining behind to prepare the yolk for assimilation by the embryo. 

After the blastoderm is formed it is one cell thick and covers the 
entire surface of the egg, with the exception of the ovarian yolk. 
The germ band originates in the region of the ovarian yolk, where 
it invaginates and grows downward into the egg. The germ band 
is of the completely submerged type, the uninvaginated blastoderm 
becoming the serosa. 

Upon leaving the surface of the egg the germ band leaves behind 
it a group of cells embedded in a mass of protoplasm. This body 
the junior author has termed the ''polar organ." 



NATURAL ENEMIES. 



103 




The development of the embryo can be observed in a general way, 1 
with a hand lens, up to and including the sixth stage. This stage is 
reached, under favorable weather conditions (50° 
to 75° F.), in about three days. 

A large number of embryos are nearly or quite 
half grown by the time freezing weather begins, 
growth starting again with the first warm days 
of February. We have noted a revolution of the 
embryo within the egg, and this revolution takes 
place between figures 1 and 2 of Plate VII. Eggs 
begin to hatch by the last week in March, the 
typical appearance of the abandoned eggshell being shown in text 
figure 18. The number of stem mothers to appear in spring depends 
to a large extent upon the temperature of the preceding fall. 

Abbreviations Used in Plates III-VII. 



Fig. 18— The spring 
grain-aphis: Shell of 
egg after young stem- 
mother has emerged. 
Greatly enlarged. 
(Original.) 



A., anterior pole. 

ab 1 , ab 2 , etc., abdominal segments. 

ab. r. abdominal region. 

am., amnion. 

app., appendage. 

at., antenna. 

6. c, blastoderm cell. 

6., blastoderm. 

c. L, cephalic lobes. 

d. o., dorsal organ. 
ec, ectoderm. 
en., entoderm. 

g. b., germ band. 
I., labrum. 
lab., labium. 
md., mandible. 



ms., mesoderm. 

mx., maxilla. 

o., fundament of ovary. 

o. y., ovarian yolk, 

p., posterior pole. 

p. o., "polar organ." 

p. p., peripheral protoplasm. 

p. y., primary yolk. 

pcd., proctodeum. 

s., serosa. 

s. g., salivary gland. 

St., stomodseum. 

th. app 1 , 2 , etc., thoracic appendages 

th. r., thoracic region. 

y. c, yolk cells. 



NATURAL ENEMIES. 

Toxoptera graminum is beset by a host of foes, without which we 
would be powerless to combat it. These enemies naturally group 
themselves into two classes: First, insects that develop within the 
body of the " green bug" and are termed true parasites; secondly, 
those foes that feed upon them externally or that take them directly 
into their bodies. These latter are termed predatory enemies. Under 
the true parasites we have Aphidius testaceipes Cress., ApJiidius ave- 
napMs Fitch, Aphidius confusus Ashm., Aplielinus mdli Hald., Aphe- 
linus nigritus How., and Aphelinus semiflavus How., all of which are 
minute four- winged flies; under predatory enemies there are lady- 
beetles, syrphids, and cecidomyiids (two-winged flies), lacewing flies, 
and birds. Besides these, there are secondary parasites, or those that 
prey upon the true parasites of Toxoptera. These latter are as truly 
our enemies as are Toxoptera. 



104 



THE SPRING GRAIN-APHIS OR 



INTERNAL OR TRUE PARASITES. 

Aphidius testaceipes Cress. 
(Fig. 19.) 

Synonyms: Lysiphlebus abutilaphidis Ashm.; Lysiphlebus bacc'haraphidis Ashm.; 
Lysiphlebus basilaris Prov.; Lysiphlebus citraphis Ashm.; Lysiphlebus coquil- 
letti Ashm. ; Lysiphlebus cucurbitaphidis Ashm. ; Lysiphlebus craufordi Rohwer; 
Lysiphlebus eragrostaphidis Ashm.; Lysiphlebus gossypii Ashm.; Lysiphlebus 
myzi Ashm.; Lysiphlebus minutus Ashm.; Lysiphlebus persicaphidis Ashm. 
(=L. persiaphidis Ashm.); lysiphlebus piceiventris Ashm.; Lysiphlebus' tritici 
Ashm. 

DESCRIPTION AND IDENTITY. 

Female. — Piceous or shining black, smooth and polished, impunctured; mandibles 
and palpi pale; antennae brownish-black, sometimes more or less pale beneath, 




Fig. 19.— Aphidius testaceipes, principal parasite of the spring grain-aphis: Adult female and antenna of 
male, greatly enlarged. Egg at right, highly magnified. (From Webster.) 

13-jointed, the joints faintly fluted or grooved, the last one longest and thickest; 
wings hyaline, iridescent, stigma pale; legs, including coxa?, yellowish-testaceous, 
the posterior pair generally more or less fuscous or blackish; abdomen often brown 
or pale piceous, with the first and sometimes part of the second segment more or less 
testaceous. Length, 0.07 inch. 

Habitat. — Rockledge, Fla.; Selma, Ala.; and Pocomoke City, Md. 

Parasitic upon an aphidid infesting twigs of orange, an aphidid on the cotton 
plant, and Aphis avense Fab. 

This parasite, which is probably the most important of all the nat- 
ural enemies of Toxoptera, has for this reason claimed more of our 
attention than all of the other foes combined. Hence a large amount 
of data has been collected, bearing upon nearly every phase of its 
development. Owing to the fact that large numbers of individuals 
have been reared by Messrs. Kelly and Urbahns from known par- 



PARASITE, APHIDIUS TESTACEIPES. 105 

ents, both parent and offspring being preserved, Mr. H. L. Viereck, 
of this bureau, has been able to determine definitely for us the iden- 
tity of this species and to clear up the obscurity heretofore surround- 
ing it. He finds that it has been masquerading under 14 different 
names, and it seems that it may now be allowed to assume its right- 
ful designation. 

Mr. Viereck, after a careful study of all material at hand, has sup- 
plied us with the above list of synonyms. His work on the revision 
of the genera Aphidius, Lysiphlebus, and Diaeretus will appear later 
in some other publication. 

LIFE HISTORY. 
OVIPOSITION. 

Under favorable conditions the females begin ovipositing within a 
few hours after issuing, whether a male is present or not. When 
the female is placed in the presence of Toxoptera she will rush about 



Fig. 20. — Aphidius testaceipes ovipositing in the body of the spring grain-aphis. Enlarged. (From 

Webster.) 

in an excited manner and when her antennae come in contact with an 
aphis she stops very quickly and thrusts her abdomen beneath her 
thorax and head (see Hg. 20), giving the aphis a quick stab — some- 
times several if the first attempts were unsuccessful; she oftentimes 
lifts the smaller plant-lice completely from the leaf, they are stabbed 
so fiercely. The act of oviposition shown in the illustration is not 
intended to convey the impression that the Aphidius always attacks 
the grain aphis at this point, as it will stab it from any position; it 
will oftentimes reach around the margin of a leaf and pierce an aphis 
on the opposite side. After being stung the aphidids kick up the pos- 
terior part of the abdomen as though in pain, and sometimes a tiny 
drop of fluid will appear at the tip of the cornicles. At no stage do 
the aphidids appear to be exempt from attack. The Aphidius readily 
attacks the winged, but apparently prefers the wingless forms. 

If parasites are confined with plant-lice for quite a while they will 
stab them repeatedly, though we have never reared more than one 
individual from the body of an aphis. It is very probable that in 
cases of this kind it is the survival of the fittest, the strongest Aphidius 
larva devouring all of the others. The junior author and Mi". W. R. 



106 THE SPRING GRAIN-APHIS OR " GREEN RUG." 

Walton, of this bureau, observed a larva, taken from the body of a 
"green bug," to apparently feed upon another larva of the same species 
that was resting against it. This would seem to indicate a tendency 
toward cannibalism. The parasites have been observed apparently 
ovipositing in aphidids that were already dead from parasitic attacks, 
those killed by fungus, and sometimes even puncturing the leaves 
of the plants on winch Toxoptera were located. 

The period of oviposition varies from 3 days to a week or more, 
depending upon the temperature. In warm weather the females will 
easily live and oviposit for 5 or 6 days. 

LENGTH OF PERIOD PROM EGG TO ADULT. 

Messrs. Kelly and Urbahns found that at Wellington, Kans., from 
7 to 15 days are consumed in passing from egg to adult during 
August and September, while for October and the first week in 
November it requires from 8 to 24 days. These figures are to a slight 
degree artificial, as the rearings upon which they are based were 
conducted indoors. The room was heated by a stove, during the day 
only, for a part of October and November, and all fire was extin- 
guished at night, so that the temperature at night probably went 
almost as low as out of doors, the house being only a small two- 
room structure. 

The average for August and September is 11.1 days; the average 
for October and November (first week) is 19 days, the average for 
the whole period being 15.9 days. These averages were made up from 
observations on 116 individuals and are therefore of more value 
than they would be if made from a few individuals only. 

At Richmond, Ind., the period from egg to adult out of doors varies 
from 10 to 14 days during August and September, while Toxoptera 
that were parasitized during November of 1907 and kept out of doors 
did not give up adults until the 27th and 28th of March and the 4th of 
April, 1908, a period of over 4 months. 

EFFECT OF PARASITISM BY APHIDIUS UPON DEVELOPMENT OF HOST. 

It has been found, as previously stated, that at no time from birth 
to and including the adult stage is Toxoptera exempt from attack by 
Aphidius. It appears that a female Aphidius prefers to oviposit in 
Toxoptera of the second and third instars. The parasite apparently 
shows little or no fear of.them at this stage, while if she is among a 
number of adult Toxoptera and they begin to kick up their abdomens, 
she often hurries away, apparently in alarm. 

It appears from our observations that Toxoptera stung before the 
first or second molt will not reach maturity, nor will the developing 
parasite become adult, there being apparently insufficent nourish- 
ment contained in such small individuals. Aphidids parasitized after 



PARASITE, APHIDIUS TESTACEIPES. 107 

the second molt will become adult, but may be either winged or 
wingless; the wings in such cases often being imperfect. Oftentimes 
parasitized aphidids reach the third molt, but do not become adult 
before death, though the parasite reaches maturity, and it is probable 
that such Toxoptera were parasitized just before casting the second 
molt. This may also account for some of the small individuals among 
the parasites. 

EFFECT OF PARASITISM BY APHIDIUS UPON FECUNDITY OF HOST. 

Experiments have been conducted with the view of learning the 
number of young that may be produced after parasitization. Tins 
can probably be best illustrated by Table XII. 



108 



THE SPRING GRAIN-APHIft OR " GREEN BUG, 



I 



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Oct. 27 
Oct. 20 


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Total 
young. 


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PARASITE, APHIDIUS TESTACEIPES. 109 

Two adult Aphidius issued from those individuals included in the 
first section of the table and 18 from those in the last section. In this 
latter section Aphidius began to issue March 30 and the last issued on 
April 3. Those that issued on the latter date were from those that 
were adult winged adults when parasitized. 

xW\ of these experiments were conducted indoors, and those of the 
last division of Table XII, under a daily temperature ranging from 
50° to 80° F. 

From Table XII it will be seen that Toxoptera that have molted 
only twice before being parasitized may become winged adults, and 
in some instances produce young. All of our observations show that 
individuals that have molted three times and then been parasitized 
will become adult and produce young, and in case they are wingless 
they may produce 10 or more. Eleven is the maximum number of 
young, according to our observations, produced by a single individual 
after parasitization. 

MOVEMENT OF LARVA WITHIN THE HOST AND MANNER OF ATTACHING IT TO THE PLANT. 

Observations were made upon the movements of the larva (fig. 21') 
within the host by the senior author at Manhattan, Kans., in 1907, and 
published in the Proceedings of the Entomological Society of Wash- 
ington. 1 

It appears that the larva of the parasite, at least until after it 
attains some growth, moves little if at all within the body of the host, 
and thus interferes with no vital functions of the Toxoptera. 

When the larva nears maturity, as shown by the yellowish color of 
the abdomen of the " green bug," it becomes quite active, making a 
number of revolutions within the body of its host, at which time the 
latter seizes the leaf with a rigid death-grip and the last spark of life 
soon fades. The object of the revolutions is, apparently, to mold the 
bod} T wall of the aphidid, while it is still plastic, into the most suitable 
shape for pupation. An idea of how this desired end is accomplished 
may be obtained by glancing at the accompanying illustrations. 
Figure 22 shows the normal position of the parasitic larva within the 
body of the host before the revolutions begin. It was found that a 
fully developed larva (fig. 23) made three revolutions within the body 
of the host, always going forward, in the space of 35 minutes. During 
the next 5 minutes it made another revolution; a fifth revolution was 
completed in the next 10 minutes; the sixth during the following 8 
minutes; the seventh in the next 9 minutes; the eighth after a space 
of 4 minutes; the ninth in the following 4 minutes, after which, on 
account of the opaqueness of the walls of the host, no further count 
was kept of the revolutions, although several more were known to 
have been made. Some of these different positions of the larva and 

I Proc. Ent. Soc. Wash., vol. 9, Nos. 1-4, pp. 110-114, 1907. 



110 



THE SPRING GRAIN-APHIS OR 



the shapes the body of the Toxoptera assumes are graphically repre- 
sented in figure 21. At this time, or about one and one-half hours 




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after the observations were begun, the body wall of the " green bug" 
became quite dark and almost globular in form, and this shape it 
afterwards retained. 



PARASITE, APHIDIUS TESTACEIPES. 



Ill 



Mr. Kelly, of this bureau, later took up the observations at this 
point, during the fall of 1908, and published the results of his obser- 




Fig. 22.— Position of larva of Aphidius testaceipes in the body of the spring grain-aphis at the beginning of 
the change to a yellowish color. Much enlarged. (Original.) 

vations in the Proceedings of the Entomological Society of Wash- 
ington. 1 Mr. Kelly confined some aphidids that were nearly dead 

from parasite attack on a slide and 
observed them under the microscope. 
He found that as the body of the " green 
bug" takes on a brownish tint, the 
Aphidius larva within makes a longi- 
tudinal slit or opening in the ventrum 
and enlarges it until it is more or less 
oval in shape, as shown in figure 24. 

The rigid, firm manner in which Tox- 
optera grasps the object upon which 
it is resting at death apparently has the 
effect of holding it in place while the 
movements of the parasitic larva are 
going on within. When the opening is 
complete the larva begins to spin its cocoon, at the same time 
ejecting a glutinous fluid that makes the strands adhere to any object 




75^- 



Fig. 23.— Full-grown larva of Aphidius 
testaceipes taken from body of the spring 
grain-aphis as shown in figure 22. 
Much enlarged. (Original.) 



Proc. Ent. Soc. Wash., vol. 11, No. 2, pp. 64-0(5, 1909. 



112 



THE SPRING GRAIN-APHIS OR " GREEN BUG. ' ' 



with which they come in contact. The body of the aphidid is 
cemented firmly to the object upon which it finally comes to rest. 
The inner abdominal walls of the plant-louse are also lined with silk, 

which firmly adheres to them, and it may be 
that the silk also acts as a tanning substance 
for the body of the aphidid, as the latter be- 
comes leathery and is apparently impervious 
to water; the old leathery bodies of the plant- 
lice may often be found firmly attached to 
plants after a heavy rain. After the cocoon 
is completed the larva becomes quiet and in 
most cases assumes, according to the junior 
author, a position directly opposite to that 
which it assumed while feeding and develop- 
ing. Figure 22 shows a larva feeding, how- 
ever, in the reversed position; this seems to 
be unusual, the normal position being as 
shown in Figure 21, I. The larva oftentimes, 
on becoming fully developed, is in some way 
dislodged from the body of the aphidid. 
This is probably due to some interference 
while attaching the host to the leaf. These 
cases are quite numerous in badly infested fields and the larva? appar- 
ently never become adult. Figure 25 is a graphic illustration of 
one of these accidents. 

Mr. Kelly found that the pupal stage lasted from 3 to 4 days. 




Fig. 24.— Larva of Aphidius testa- 
ceipes spinning its cocoon in the 
dead body of the spring grain- 
aphis, showing the slit or open- 
ing in walls of underside of 
host insect. Much enlarged. 
(Original.) 





Fig. 25.— Larvaof A phidius testaceipes work- 
ing its way prematurely from the body of 
the spring grain-aphis . (From Webster. ) 

Figure 26 shows the larva just prior 
tions were made indoors, during the 
temperature. It requires from 3 to 



Fig. 26.— Full-grown larva of Aphidius 
testaceipes: a, Lateral view just prior to 
pupation; b, front view of head. . Greatly 
enlarged. (Original.) 

to pupation. These observa- 
winter, at the ordinary room 
5 hours for the Aphidius to 



■ 



PARASITE, APHIDIUS TESTACEIPES. 



113 



emerge as an adult after the first movements of the pupa begin, and 
when ready to issue the pupa expands and contracts the abdomen, 
moving the feet and antennae until these are freed from their gum- 
like covering. Upon studying the pupae (^.g. 27) 
closely, we find that the prothorax bears two rows 
of distinct elevations or tubercles, but we have 
been unable thus far to ascribe any particular 
function to them and they disappear with the 
gum-like covering. The junior author finds that 
the adult gradually works itself about until it gets 
in a position with its back to the ventrum of the 
old aphidid shell, when it cuts a circular hole, as 
described by Mr. Kelly, and crawls out, always 
with its head pointing toward the head of the old 
aphidid. Figure 28 represents an old dead body of 
a " green bug" after the parasite has issued. 

FECUNDITY. 




Fig. 27. — Pupa of 
Aphidius testaceipes 
immediately after 
pupation. Much 
enlarged. (Origi- 
nal.) 



From the prompt manner in which Aphidius, under favorable 
weather conditions, overcomes Toxoptera it will readily be seen that 
the former must be a very prolific breeder. The 
average adult female contains from 4 to 450 
eggs. These eggs are lemon-shaped (see fig. 
19), very pale, and translucent. 

Messrs. Kelly and Urbahns conducted a 
number of experiments at Wellington, Kans., 
in 1908, to determine the number of offspring 
produced by one individual. They found that 
one Aphidius would parasitize as many as 206 
Toxoptera. In their experiments, however, 
they used only a few more than 200 Toxoptera 
to each individual. Mr. Parks, at the same 
place in 1909, conducted 16 experiments, using 
from 300 to 500 Toxoptera and he had a maxi- 
mum, in one case, of 301 aphidids parasitized 
from one individual Aphidius. His minimum 
was 3; his next highest number was 33, and 
his next was 44. Of the sixteen, 12 fell below 
100; his average was 94.6. 

Mr. Parks also conducted experiments at the 
same time as the above to ascertain what the ef- 
fects of continuous mating of one male to differ- 
ent females would have on the offspring. In 
this experiment 1 male was mated to 12 unfertilized females within a 
period of two hours, after which each female was placed in a separate 
cage with about 100 Toxoptera that had not been exposed to Aphidius. 
26675°— Bull. 110—12 8 




Fig. 28.— Dead "green bugs" 
{Toxoptera graminum), 
showing holes from which 
the matured parasites of 
Aphidius testaceipes emerge. 
The top figure shows the lid 
still attached, but pushed 
back; the bottom figure 
shows the parasite emerg- 
ing. Enlarged. (From 
Webster.) 



114 



THE SPBING GKAIN-APHIS OR ^ GREEN BUG." 



The male refused to mate with any more females after the twelfth. 
Table XIII shows the results of these observations: 



Table XIII. — Offspring 'produced as the result of mating one 



Aphidius with 12 





Female 


Offspring. 


Female, 
cage No. — 


mated with 
male from 










cage No. — 


Males. 


Females. 


180 


180 


29 


55 


181 


180 


14 


33 


182 


180 


21 


30 


183 


180 


35 


41 


184 


180 


2 


8 


185 


180 








186 


180 


13 


30 


187 


180 


39 


25 


188 


180 


1 





189 


180 


50 





190 


180 


8 


9 


191 


180 


26 


16 



From these data it appears that all of the eggs from the last few 
females were not fertilized, as Mr. Kelly finds that females predom- 
inate when the eggs are properly fertilized. Table XIV illustrates 
this latter point. 

Table XIV. — Offspring of Aphidius produced from eggs properly fertilized. 





Offspring. 


Cage No.— 










Males. 


Females. 


197 


39 


67 


297 


15 


20 


299 


13 


33 


300 


24 


40 


302 


20 


34 


304 


16 


50 


306 


47 


12 


333 


115 


15 


403 


26 


41 


404 


38 


93 


405 
Total . . 


26 


44 


379 


429 



1 These two females were apparently unfertilized, although they were supposed to have mated, as they 
give about the same results as some of the unmated females. If these two be eliminated it will be seen that 
the females are far in excess of the males. 



PARTHENOGENESIS. 



In all of the studies of parthenogenesis care was taken to preserve 
both parents and offspring, the individuals of each family or brood 
being preserved and kept entirely separate for future systematic 
studies, which were later carried out by Mr. Viereck. 

The first record of parthenogenesis of this species was published in 
the Proceedings of the Entomological Society of Washington, 1 by 
the junior author, whose attention was first called to this phenomenon 

i Proc. Ent. Soc. Wash., vol. 10, Nos. 1-2, September 15, 1908, pp. 11-13. 



115 

during the summer of 1907, while making observations on the life 
history of the species; hence, a series of experiments was begun in 
order to learn something definite in regard to it. Seven female 
Aphidius were selected, just as they issued from their cocoons (being 
therefore unfertilized), and placed in separate cages with 30 to 40 
Toxoptera not previously exposed to parasite attack. All of the 
parasites began ovipositing at once. After one of the females had 
apparently parasitized all of the aphidids in her cage she was mated 
and placed in a second cage with a number of Toxoptera as before. 
All the offspring from unmated females were males, but the offspring 
from the single female, after she had mated, comprised 22 females 
and 4 males. 

Messrs. Kelly and Urbahns elucidated this phenomenon more fully 
during the summer of 1908 at Wellington, Kans. 1 These experi- 
ments were conducted as follows: 

Starting with a mated female, the females from among her off- 
spring were isolated, even before emergence. On their appearance 
they were given Toxoptera not previously exposed to parasitic attack. 
The few females from among this second generation were again 
isolated in the same manner, the females in all cases being kept 
unmated. Nearly 100 experiments were conducted in this manner, 
but only 48 gave results. The offspring of 44 out of the 48 isolated 
were, all of them, males. Of the 4 remaining females, the offspring 
of 3 were as follows: 70 males and 3 females; 101 males and 6 females; 
67 males and 1 female. In the case of the remaining female, some 
uncertainty exists as to whether she had been fertilized or not, and, 
for tins reason, a census of her offspring is not here included. 

Of the three exceptional cases the offspring from one female were 
not bred any further; from a second, the offspring became all males 
in the second generation ; the offspring from the third female produced 
two females in the second generation, all finally becoming males in 
the third generation. 

In this manner it will be seen that Messrs. Kelly and Urbahns were 
able to rear a limited- number of females parthenogenetically to the 
third generation. Beyond this all of the offspring were males. While 
the conditions under which these experiments were conducted would 
not obtain under ordinary field conditions where the infestation was 
great, it could very easily occur where there are very few aphidids 
present. This apparently abnormal feature, then, would greatly 
assist the species in tiding over periods of scarcity of plant-lice. 

HOSTS OP APHIDIUS TESTACEIPES. 

Since we were able to find Aphidius testaceipes over almost* the entire 
United States, it seemed clear to us that it must have hosts other than 
Toxoptera graminum. Accordingly Messrs. Kelly and Urbahns con- 

1 Ann. Ent. Soc. Amer., vol. 2, No. 2, 1909, pp. 67-87. 



116 

ducted about 200 experiments in order to gain some definite informa- 
tion on this point. Their mode of procedure was to search out differ- 
ent species of parasitized aphidids in the fields, rear the adult para- 
sites, and breed them into Toxoptera graminum; then, if possible, 
breeding them again into the original host. One attempt, if unsuc- 
cessful, was not considered sufficient, several trials being made. 
While conducting these experiments, other species of parasites were 
found that would breed into Toxoptera also. These will be dealt 
with in their proper places. In all of these breedings, both parent 
and offspring were kept separate and preserved for future study. 

It was found that Aphidius testaceipes would breed interchangeably 
from Toxoptera into Aphis setaride, Aphis maidis, Aphis middletoni 
Thos., 1 Aphis gossypii, and a species of Chaitophorus. This is the same 
as the list published by the senior author in the Annals of the Ento- 
mological Society of America, 2 with the exception that Chaitophorus 
is added and Aphis brassicse has been expunged from the list, as it 
has been learned that the species of parasite that would interchange 
with Toxoptera graminum and A. brassicse is another species of Aphi- 
dius. 

Besides the above list of interchangeable breedings, Aphidius 
testaceipes has been reared from Aphis oznotherx at Salisbury, N. C, 
by Mr. R. A. Vickery; from A. medicaginis at Wellington, Kans., by 
Messrs. Kelly and Urbahns; from A. rumicis at Clemson, S. C, by 
Mr. G. G. Ainslie; from Macrosiphum viticola at Wellington, Kans., 
by Mr. Kelly; from M. granaria at Spartanburg, S. C, by Mr. 
G. G. Ainslie; from Melanoxantherium sp. at Leavenworth, Kans., 
by Mr. Kelly; from Macrosiphum sp. on black gum (Nyssa sylvatica) 
at Salisbury, S. C, by Mr. Vickery; from Aphis avense, at Salisbury, 
N. C, by Mr. Vickery; at Leavenworth, Kans., by Mr. Kelly, and at 
Washington, D. C, by Mr. C. N. Ainslie; and from Aphis medicaginis 
by Mr. J. T. Monell, at St. Louis, Mo. Aphidius testaceipes has also 
been reared from several unidentified species of aphidids, as follows: 
From an aphidid on Ampelopsis sp. by Mr. C. N. Ainslie; from an 
aphidid on Capsella sp. at Wellington, Kans., by Mr. C. N. Ainslie ; from 
an aphidid on Kochia scoparia at Rochester, Minn., by Mr. C. N. Ainslie ; 
from an aphidid on locust at Wellington, Kans., by Mr. Kelly; from 
an aphidid on plum at Salisbury, N. C, by Mr. Vickery; from an 
aphidid on pigweed (Chenopodium album) in Olmstead County, Minn., 
by Mr. C. N. Ainslie. 

Further addition to this list of hosts may be made by citing the 
hosts of some of the synonyms of Aphidius testaceipes. 3 We will deal 

1 Aphis middletoni can not be satisfactorily separated from Aphis rnaidi-radicis and when found on any 
other plant except Erigeron it has usually been identified as Aphis maidi-radicis . (See Bui. 85, Bur. 
Ent., U. S. Dept. Agr., pp. 113-114. Contributions to a Knowledge of the Corn Root-Aphis, by R. A. 
Vickery.) 

2 Ann. Ent. Soc. Amer., vol. 2, No. 2, pp. 67-87, June, 1909. 

3 See Proc. U. S. Nat. Mus., vol. 11, pp. 065-669, 1888. 



PARASITE, APHTDIUS TESTACEIPES. 117 

with these synonyms collectively under A. testaceipes. The hosts 
then would be as follows: Reared from Macrosiphum cucurbitx by 
the senior author at Lafayette, Ind.; reared from an aphidid on 
Eragrostis sp., by Mr. D. W. Coquillett; reared from Macrosiphum 
sp. on Audibertia stochoides, by Mr. Coquillett, at Los Angeles, Cal. 
Swept from Eragrostis sp. by the senior author at La Fayette, Ind., 
October 4, 1885; reared from Myzus sp. on Hosackia glabra by Mr. 
Coquillett at Los Angeles, Cal.; reared from Myzus ribis (currant 
aplus) by Prof. A. J. Cook, Lansing, Mich..; reared from Aphis gos- 
sypii by Prof. G. F. Atkinson, Columbia, S. C; reared from Macro- 
siphum sp. on Abutilon by Mr. Coquillett at Los Angeles, Cal.; reared 
from Aphis avense by Mr. J. W. Barlow, June 20, 1882, at Cadet, Mo.; 
reared from Aplus on peach May, 1886, by Mr. Albert Koebele, 
Fresno County, Cal.; reared from an aphidid on Baccharis viminalis 
by Mr. Coquillett at Los Angeles, Cal. 

There are probably many other hosts besides the ones we have 
mentioned of which as yet we have no knowledge; and when this 
situation is taken under consideration it is very easy to see that it 
would be only in rare instances and under peculiar conditions that 
a locality would be found where Aphidius testaceipes would not be 
lurking, waiting for favorable weather conditions and abundant 
supplies of its host aphidids to make its appearance in greater or less 
numbers. 

HIBERNATION. 

Aphidius is capable of withstanding extreme degrees of cold, as 
witnessed by the fact that Toxoptera parasitized during November, 
1907, at Richmond, Ind., did not give up adults until the 27th and 
28th of March and the 4th of April following. During February they 
were in the larval stage within an old dead body of a Toxoptera. 

Mr. Kelly found that at Leavenworth, Kans., the parasites hiber- 
nated as larvae and pupae. This was shown by the fact that he found 
Aphidius testaceipes in the field in this condition on November 13, 
1907. From a lot of 50 dead parasitized Toxoptera from the same 
field, that had been washed or rubbed off the leaves of the young 
grain and were taken out of the mud about the wheat; plants on 
February 28, after the winter was practically over, Mr. Kelly found 
that 17 contained full-grown larvse, 12 contained pupae of a light 
color, and 21 contained pupae of a dark color; the latter apparently 
were ready to develop promptly with the advent of warm weather. 
Mr. Kelly collected, on the same date and also from this same field, 
a number of Toxoptera in various stages of development that were 
hibernating in the fields and which showed no signs of parasitism; 
the weather had been such as to preclude the possibility of their 
having recently been parasitized. These were placed in a warm 
room and soon showed evidence of parasitism, Aphidius testaceipes 
being finally reared from them. 



118 

The junior author found that at Kichmond, Ind., the adult Aphid- 
ius would live for at least two weeks when the temperature was 
below freezing. The parasites were taken into a warm room several 
times during these two weeks and they would become active, but 
when placed out of doors they would soon become numb. These 
adults were confined, however, so that excessive moisture was 
excluded, and they may not be able to live for so long a time in the 
fields unprotected. 

The fact that Aphidius can during comparatively cold weather 
remain for a long period within the body of its host, and the latter 
give no external visible evidence of its presence, will readily account 
for the apparent absence of the parasite from any locality for an almost 
indefinite period; however, when the weather warms up sufficiently 
for development of the parasite to go on, its presence readily becomes 
apparent. For these reasons, as well as others that will be men- 
tioned in their proper places, it is impossible to say, from a cursory 
examination, that Aphidius is not present. 

INFLUENCE OF WINDS IN THE DISPERSION OF APHIDIUS TESTACEIPES. 

As the natural suppression of an outbreak of Toxoptera is more 
dependent upon the activity of this parasite than of any other of its 
natural enemies, it is important to learn the extent to which the para- 
site is able to follow its host in its spread from the South over the 
country to the northward. 

Dispersion of Aphidius may be accomplished in two ways — first, 

as larvae in the bodies of the 
winged host insect, where it is 
usually invisible, and, second, 
by being carried bodily with the 
winds along with the host. 

By referring to Table XII on 
page 108, it will be observed that 
a number of cases are there 
recorded where individuals of 
Toxoptera qraminum which were 

Fig. 29. — Winged female of the spring gram-aphis, ••tit 

parasitized by Aphidius testaceipes. Enlarged. parasitized developed to Winged 
(From Webster.) ^^ liyed f()r ft period of 

eight or nine days, and during this time gave birth to young, but 
from their dead bodies Aphidius afterwards issued. The pres- 
ence of winged parasitized females on the leaves of grain and grasses 
inhabited by Toxoptera is of common occurrence (see fig. 29). Thus, 
while it has not been possible to observe the parasitism of individuals 
and follow out the final dispersion of the same, the evidence tending 
to show the probability of its general occurrence is so overwhelming 
that such direct proof does not seem necessary. With the obscurity 




PARASITE, APHIDIUS TESTACEIPES. 119 

relative to this matter cleared away, it will be observed that it is 
entirely possible for great numbers of the adults, or those that are 
nearly mature, to become parasitized in a southern locality, the 
latter to develop to winged females under a more or less high 
temperature, and for both to be carried many miles to the north- 
ward, and then settle down and begin to reproduce, the Aphidius 
becoming adult and issuing later from the dead body of its host. In 
the meantime the offspring of the host Toxoptera would, of course, 
develop and themselves reproduce, some of them, without doubt, falling 
victims to the very parasite brought along by their parent. While 
tins may not be the chief factor in the dispersion of this parasite, it 
probably enables it to follow along with the host insect and become 
diffused with it, although if low temperatures prevail after the time 
the migrating female settles in her new home there may be consider- 
able delay in the issuing of the adult parasite without to any great 
extent delaying the development and preventing the increase of 
Toxoptera. 

With the temperature at a point which enables Aphidius to become 
active there is no doubt that the parasite follows with the host insect, 
and, indeed, these parasites are usually found on the wing in the com- 
pany of their hosts during warm sunny days. With high cold winds, 
which usually come from the northward and would tend to drive the 
parasites back over territory to which Toxoptera has already come 
and from which it has now largely disappeared, the adult Aphidius 
is observed to nestle down among the infested plants and not to 
venture abroad. Thus it is that this parasite is doubtless usually 
present in some form in the grain fields with the Toxoptera, though 
critical examinations of such fields may fail to reveal them until the 
temperature reaches a point that enables them to become active. 

All of this is applicable to the insect in southern territory where no 
egg stage is yet known to occur. Aphidius occurs all over the coun- 
try, and we have learned that in the North it winters as fully devel- 
oped larvae and pupse within the "cocooned" bodies of its* hosts, its 
emergence and activity in spring being controlled by the temperature 
and its dispersion influenced by the same forces and in much the same 
manner as in the South. 

TEMPERATURE INFLUENCES ON APHIDIUS. 

Probably the whole secret of these disastrous outbreaks of Tox- 
optera lies in the fact that this parasite is not active in a tempera- 
ture much below 56° F., while, as has already been shown, the aphis 
begins to reproduce in a temperature at or slightly below 40° F. — 
a probable difference of at least 16° F. Therefore the situation in a 
field of wheat in the South in early spring may be described in this 
way: There are present many Toxoptera of all ages, with viviparous 



120 THE SPRING GRAIN-APHIS OR " GREEN BUG." 

reproduction continually going on during mild weather. Aphidius 
may also be present either as invisible undeveloped overwintering 
larvae within the living bodies of its host, or it may be present as 
mature larvae or pupae in the dead and dried "cocooned" bodies of 
the same. Besides this, in the light of recent studies of Aphidius by 
Mr. Viereck, the same may be true with reference to its occurrence in 
a considerable number of other common species of aphidids, inhabit- 
ing a great variety of vegetation, in the same neighborhood, upon 
which this same species of Aphidius is parasitic. Thus, it is per- 
fectly clear why, with Toxoptera swarming in the fields, and the 
parasite present, about 10 days, with the temperature ranging from 
40° or 50° to 60° or 70° F., is sufficient to enable the latter summarily 
to suppress the invasion. The abruptness with which this change is 
brought about is easily explained by the fact that a parasitized female 
Toxoptera produces young during only a comparatively few days after 
being parasitized, although she may survive several days longer, 
especially if the weather be cool enough to retard the development 
of the parasite. 

In the North the situation is usually quite different, as parasites 
can not begin their work here to any extent until after the eggs have 
hatched, and the stem mothers and their offspring have appeared in 
the fields, thereby furnishing host insects. The overwintering of 
immature Aphidius larvae in the bodies of the host is in the North 
ordinarily precluded by the absence of living host individuals during 
severe winters, although mature larvae may winter in the dead bodies 
of the host as in the South. Stem mothers are probably never 
present in great numbers and considerable time is therefore neces- 
sarily required for their offspring to become excessively abundant. 
For this reason parasitism, over the section where the host insects 
pass the winter in the egg, begins later, and, at the start, proceeds 
necessarily much slower than in the South, but on the other hand 
Aphidius, unless the winter be an exceptional one, must of necessity 
winter over in the "cocooned" bodies of its numerous hosts, as 
mature larvae or pupae, and would therefore promptly respond to 
the warm days of early spring, although delayed somewhat by 
low temperatures that might not retard the host insects. 

There is one point in connection with parasitism by Aphidius that 
must be always kept in view, particularly to the southward, in order 
that mistakes and misstatements may be avoided regarding its 
actual occurrence in any particular locality. While the larva is 
contained within the still living body of its host its presence there is 
not easily detected. Indeed it is not until the larva becomes nearly 
full grown that it can be detected even by an expert. Therefore, 
in the light of what has previously been stated concerning the situa- 
tion in milder latitudes, there may be millions of living larvae 



PARASITE, APHIDIUS TESTACEIPES. 121 

present for weeks in a field with no visible indication of their presence. 
Yet only a few warm days are required to bring about their final 
development, whereupon the presence of the more or less globular, 
leathery, brown bodies of the parasitized host first begin to attract 
attention and thus actually reveal the presence of the Aphidius, 
which has already been established there. 

An excellent illustration of this is afforded by an occurrence of 
Toxoptera in eastern North Carolina, observed by Mr. L. M. Smith. 
In a small field of oats near Newport, wingless viviparous female 
Toxoptera and young were found in destructive abundance with no 
indication whatever of the presence of Aphidius. Yet when speci- 
mens of the pest submitted by Mr. Smith reached Washington, some 
of them were beginning to change color from the presence of Aphidius 
larvae within their abdomens. Again, when Mr. C. N. Ainslie visited 
Wellington, Kans., April 1, 1907, he observed no trace of the presence 
of Aphidius, but upon returning to this same locality on April 10 he 
found them present. Only a few of the Toxoptera had yet become 
dark brown, but a large number showed the orange color that told 
the story of their parasitism. Therefore all statements made in 
previous publications relative to the lack of parasites, or to the 
extent to which they occurred in any field or locality, must be under- 
stood as applying only to either the adults or to the browned cocooned 
bodies of the host insects, and are not in any sense to be considered 
as indicating the extent to which these host insects were carrying 
obscured Aphidius larvae about with them in their bodies to develop 
adults whenever there were a few sufficiently warm days. 

EFFECTS OF WET WEATHER ON THE DIFFUSION OF APHIDIUS. 

There is another element affecting the diffusion of this most 
efficient of natural enemiss of Toxoptera, namely, protracted rains. 
When it is raining the parasite simply will not take wing at all or 
move about in a way to be affected by winds. This element will 
not admit of tabulation for the reason that a thunder shower followed 
by warm, bright sunshine tends to make these, as well as all winged 
insects, more active after the storm has passed. Thus, the amount 
of precipitation really means little, while a slow, drizzling, protracted 
rain (though the total precipitation may be much less) will keep the 
parasite in seclusion much more effectively. Hence it is that not 
only a comparatively high temperature accompanied by winds is 
essential, but the weather must also be fair and sunny. 

In British East Africa Toxoptera is worse during seasons when 
there is much wet weather, and in the Orange Free State outbreaks 
of the pest seem to be also associated with similar meteorological 
conditions during spring. 



122 THE SPRING GRAIN-APHIS OR " GREEN BUG." 

Other Species of Aphidius. 

Aphidius confusus Ashm. has been reared from Toxoptera from 
different parts of the country, including the Department of Agri- 
culture grounds in Washington, but to what extent it assisted in 
overcoming Toxoptera in 1907 is not altogether clear. Its life 
history is apparently similar to that of A. testaceipes Cress., and its 
effect upon the aphides is apparently the same. 

Aphidius avenaphis Fitch was reared from Toxoptera graminum in 
the insect ary at the Department of Agriculture in Washington, the 
host insect having been parasitized, under observation, by adult 
virgin Aphidius reared from Aphis sp. 




Fig. 30.— Aphelinus mali, a parasite of the spring grain-aphis. Greatly enlarged, a, Stigmal club, 
much more enlarged. (Original.) 

Species of Aphidius, apparently undescribed, were sent to the 
bureau from Njoro, British East Africa, and the Orange Free State, 
South Africa, as enemies of Toxoptera graminum in that country. 

Aphelinus. 

We have reared three species of Aphelinus from Toxoptera grami- 
num; Aphelinus mali Hald., A. nigritus How., and A. semiflavus 
How. 

Aphelinus mali Hald. (fig. 30) was reared from Toxoptera at 
Lafayette, Ind., in 1885 by the senior author, by Mr. K. A. Vickery 
at Richmond, Ind., and from the same species at Clemson, S. C, by 
Mr. G. G. Ainslie. Messrs. Kelly, Urbahns, and Parks reared it from 
Aphis setarise Thos. at Wellington, Kans. Messrs. Kelly and Urbahns 
also reared it from Schizoneura americana Riley at Wellington. Mr. 
Vickery reared it from Schizoneura lanigera Haussm. at Richmond, 



PARASITES, APHELINUS. 



123 



Ind., and from Colopha eragrostidis Middl. at Mt. Vernon, Ind. 
Mr. Kelly reared it from Pemphigus fraxinifolii Kiley and from an 
aphidid taken on Panicum sp. Mr. C. N. Ainslie reared it from 
Macrosiphum rosse Linn., at Mesilla Park, N. Mex. 

This species has been previously reared, as stated by Dr. L. O. 
Howard 1 from Schizoneura lanigera Haussm., Colopha eragrostidis 
Middl., Aphis brassier Linn., Pemphigus fraxinifolii Riley, Aphis 
monardx Oestl, Macrosiphum rosse Linn., Aphis sacchari Zehntn., and 
Tetraneura colophoidea. 

Aphelinus nigritus How. (fig. 31) was first reared from Toxoptera 
at Spartanburg and Clemson, S. C, by Mr. G. G. Ainslie. It was 




Fig. 31.— Aphelinus nigritus, a parasite of the spring grain-aphis. Greatly enlarged, a, Stigmal club, 
still more enlarged. (Original.) 

reared from the same species of aphidid by Mr. C. N. Ainslie at 
Springer and Mesilla Park, N. Mex., and St. Anthony Park, Minn. 
Mr. T. H. Parks reared it from Toxoptera at Wellington, Kans., and 
Messrs. Kelly and Urbahns reared it from Aphis setarist Thos. at 
Wellington. 

Aphelinus semiflavus How. (fig. 32) was first reared from Myzus 
persicse Sulz. and Chaitophorus viminalis Monell by Prof. C. P. Gil- 
lette at Fort Collins, Colo., in 1908. It was later reared by Mr. G. G. 
Ainslie from Toxoptera at St. Anthony Park, Minn., and from a 
black aphidid on bluegrass (probably Rhopalosiphum pose Gill.) at 
Mesilla Park, N. Mex., by C. N. Ainslie. 

i Ent. News., vol. 19, no. 8, pp. 365-36G, 1908. 



124 



NOTES ON LIFE HISTORY AND HABITS OF APHELINUS. 

Mr. C. N. Ainslie made some observations on Aphelinus nigritus 
at Mesilla Park, N. Mex., in 1908. He states that when the adult is 
ready to oviposit it approaches an aphidid very slowly and cautiously, 
moving or swaying its body slightly from side to side and waving its 
antennas. When the antennas finally touch the plant-louse it stops, 
turns suddenly about, moves backward slightly, and then gives the 
victim a thrust with its hairlike ovipositor. This operation appar- 
ently causes pain to the aphidid, as she begins to "kick up" her 
abdomen and there sometimes appears a tiny drop of fluid where the 
puncture was made. 




Fig. 33.— Dried remains of 
body of the spring grain- 
aphis from which adult 
Aphelinus nigritus 
emerged. Enlarged. 
(Original.) 



Fig.32. — Aphelinus semiflavus, a parasite of the spring grain-aphis. Greatly- 
enlarged, a, Stigmal club, still more enlarged. (Original.) 

When the larva of Aphelinus nigritus is fully grown the body of the 
plant-louse, according to Mr. G. G. Ainslie, turns black and the legs a 
conspicuous white (fig. 33), while in individuals parasitized by A. 
mali these appendages are black. The body, however, of so small 
an aphidid as Toxoptera graminum appears to be but little swollen. 
Mr. C. N. Ainslie found that under favorable weather conditions A. 
nigritus developed from egg to adult in from 12 to 13 days. 

The following diagram will serve to illustrate the different hosts of 
Aphidius testaceipes, A. avenaphis, A. confusus, Aphelinus mali } 
A. nigritus j and A. semiflavus, which we have shown to attack 
Toxoptera graminum. This will give some idea of the numerous 
sources from which an army of parasites may be recruited to oppose 
any serious invasion of Toxoptera. 



SECONDABY PARASITES. 



125 



Toxoptcra graminum 1 



Aphidius. 



Aphelinus.. 



avenaphis. . Macrosiphum granaria Buck. 
confusus. . . Macrosiphum erigeronensis Thos. 
testaceipes . . Aphis avenx Fab . 

Aphis gossypii Glov. Aphis sp. 

Aphis maidis Fitch. 

Aphis maidi-radicis Forbes. 

Aphis medicaginis Koch. 

Aphis aznoiherx Oestl. 

Aphis rumicis Linn. 

Aphis setarix Thos. 

Macrosiphum viticola Thos. 

Macrosiphum granaria Buckt. 

Melanoxantherium sp. 

Macrosiphum sp. on black gum. 

Myzus ribis Linn, on currant. 

Myzus sp. on Hosackia glabra. 

Macrosiphum sp. on Abutilon. 

Macrosiphum cucurbitx Thos. 

Aphidid on Ampelopsis sp. 

Aphidid on Baccharis viminalis. 

Aphidid on Capsella bursa-pastoris . 

Aphidid on Eragrostis sp. 

Aphidid on Kochia sp. 

Aphidid on locust. 

Aphidid on peach. 

Aphidid on pigweed (?). 

Aphidid on plum. 

mali Aphis brassicx Linn. 

Aphis monardx Oestl. 

Aphis sacchari (?) Zehntn. 

Aphis setarix Thos. 

Colopha eragrostidis Middl. 

Myzus mahaleb Boyer. 

Pemphigus fraxinifolii Riley. 

Macrosiphum rosx Linn. 

Schizoneura americana Riley. 

Schizoneura lanigera Haussm. 

Tetraneura colophoidea (?). 

nigritus Aphis setarix Thos. 

semi jlav us.. Aphis maidis Fitch. 

Aphis gossypii (?) Glover. 

Chaitophorus viminalis Mon. 

Myzus persicx Sulz. 



SECONDARY PARASITES. 



Megorismus sp. 

Species of the genus Megorismus-, it appears, have been previously- 
considered as primary parasites. Mr. Parks, however, has con- 
ducted some experiments with a species (fig. 34) at Wellington, 
Kans., and his results clearly indicate that in this case it is a sec- 
ondary parasite. In no instance could he rear it from aphidids 



126 

that had not previously been parasitized; he experienced no diffi- 
culty, however, in rearing it when the adults were placed in cages 
with aphidids that were brown, having been killed by some species 
of Aphidius. It may be that under certain conditions Megorismus 
sp. is also a primary parasite. Mr. Parks finds that it takes about 
30 days in developing from egg to adult in a temperature of about 
70° F. indoors. 

It has been reared in conjunction with Aphidius sp. from Toxoptera 
graminum and Chaitophorus sp. at Wellington, Kans., by Messrs. 
Kelly and Urbahns; from T. graminum and Aphis brassiest in the 
same locality by Mr. Parks. Mr. Parks also reared it from Macrosi- 




FlG. 34. 



■Megorismus sp., a secondary parasite of the spring grain-aphis: Male, greatly enlarged; female 
abdomen, more enlarged, at right. (Original.) 



phum pisi at Washington, D. C. Mr. C. N*. Ainslie reared it from 
Hyalopterus dactylidis in the same locality, and the junior author 
reared it from Myzus persicse at Lafayette, Ind. 

Aphidencyrtus aphidiphagus Ashm. 

The species Aphidencyrtus aphidiphagus Ashm. (fig. 35) has also 
been considered a primary parasite, and while we have no direct 
evidence to disprove this we very strongly suspect that it is in this 
case a secondary parasite. Like Megorismus, which, we have shown, 
is sometimes, at least, a secondary parasite, we have reared it only 
in conjunction with known primary parasites. Mr. G. G. Ainslie 
could rear it only in connection with Aphelinus sp. from T. graminum 
at Clemson, S. C, and Mr. C. N. Ainslie reared it from Aphis 



SECONDARY PARASITES. 



127 



hrassicse at Mesilla Park, N. Mex., in conjunction with ApTiidius sp. 
Nothing definite is known of its life history. 

Pachyneuron sp. 

A species of Pachyneuron (fig. 36) has been repeatedly reared from 
Toxoptera graminum and it appears to be generally accepted as a 




Fig. Zo.—Aphidcncyrtus aphidiphagus, a secondary parasite of the spring grain-aphis. Greatly- 
enlarged. (Original.) 

secondary parasite. Mr. Kelly has observed it ovipositing in brown 
parasitized MacrosipTium viticola. Mr. G. G. Ainslie reared it in con- 
junction with Aphelinus sp. from Toxoptera and with ApTiidius sp.from 




Fig. 30.— Pachyneuron sp., a secondary parasite of the spring grain-aphis. Greatly enlarged. (Original.) 

ApTiis maidis from Clemson, S. C. ; and from Toxoptera at St. Anthony 
Park, Minn. Mr. C. N. Ainslie reared it in connection with ApTiidius 
sp. from Apliis setarise, A. gossypii, Macrosiplium granaria, and 
J/, erigeronensis and in connection with Aphelinus sp. from Scliizo- 



128 



THE SPRING GRAIN-APHIS OR GREEN BUG. 



neura americana. He also reared it from Macrosiphum viticola and 
Chaitophorus sp. Pachyneuron sp. appears to be quite generally dis- 
tributed but little or nothing is known of its life history. 

Allotria sp. 

Allotria sp. (fig. 37) is recorded as a secondary parasite. Mr. 
Parks verified this by careful rearings at Wellington, Kans., in 
1909, for he was able to rear it only from parasitized aphidids. The 
junior author and Messrs. Kelly and Urbahns have observed it 
ovipositing in parasitized dead aphidids also. Mr. Parks found in 
his experiments that it developed from egg to adult in about 21 

days, under favor- 
able temperatures. 
We have reared 
it only in conjunc- 
tion with Aphidius. 
Messrs. Kelly and 
Urbahns reared it 
from Aphis gossypii 
and A. brassicse at 
Wellington, Kans. ; 
Mr. Parks reared it 
from Toxoptera 
from the same local- 
ity; Messrs. Parks 
and Kelly also 
reared it from Tox- 

Fig. 37.— Allotriasj)., a secondary parasite of the spring grain-aphis. Male, optera at Washjng- 
with female antenna at upper right. Greatly enlarged. (Original.) , -n n Tyr r\ 

N". Ainslie reared it from Aphis avense and Hyalopterus dactylidis from 
the same locality. Mr. Kelly reared it from Macrosiphum viticola 
from Wellington, Kans., and the junior author reared it from Myzus 
persicx at Lafayette, Ind. 

PREDACEOXJS ENEMIES. 

Lady-beetles. 

Probably next in importance to the genus Aphidius come the 
ladybird beetles. These beetles, in both the adult and larval stages, 
feed upon plant-lice. In 1907 they became very abundant, destroy- 
ing countless numbers of Toxoptera and greatly assisted Aphidius in 
subduing the pest. Plate VIII represents the manner in which the 
pupae are found attached to plants in fields badly infested with 
Toxoptera; to the left is a 2-inch section of an old cowpea stem; to 
the right, two short sections of wheat stems. Oftentimes as many 
as 30 or more pupae could be found within the space of a foot of a 
single drill row. Adults deposit eggs upon any convenient object. 







Bui. 1 1 0, Bureau of Entomology, U. S. Dept. of Agriculture. 



Plate VII. 



cr 




to 
cr 

ll- 




IL 




L 




* .2 « 
m 53 •- 

ot a> ^ 

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ll, 110, Bureau of Entomology, U. S. Dept. of Agriculur 



Plate VII! 




A Lady-Beetle Enemy of the Spring Grain-Aphis. 

Pupae of Hippodamia convergent attached to stem of cowpea and wheat straws in a field where the spring 
grain-aphis had been excessively abundant. Enlarged. (Original.) 



PREDACEOUS ENEMIES. 



129 



and, as soon as hatched, the larva seem possessed of an insatiable 
appetite, devouring aphidids or even eggs and larvae of their own 
species if no plant-lice are at hand. Mr. Kelly has found that an 




Fig. 3S.— The convergent lady-beetle ( Hippodamia convcrgens) , an enemy of the spring grain-aphis: a, Adult; 
b, pupa; c, larva. Enlarged. (From Chittenden.) 

adult ladybird (Hippodamia convergens) (fig. 38) will devour from 15 
to 30 plant-lice in a day. Mr. S. J. Hunter, in ' ' The Green Bug and its 
Enemies," page 6, states that instances have come under his observa- 
tion where as many as 100 have been devoured in a single day by an 
adultlady-beetle. The larvae when nearly 
grown are probably able even to exceed 
this record. In one of Mr. Kelly's experi- 
ments a single beetle deposited as many 
as 264 eggs, thus showing that this lady- 
bird is very prolific. "When all of these 
facts are considered it is 
easy to see that the lady- 
beetles are rather formida- 
ble enemies of Toxoptera. 
Hippodamia convergens 
appeared to be by far the 
most abundant ladybird 
in the Southwest in 1907. 

Coccinella 9-notata (figs. 39, 40) and Megilla maculata 
(fig. 4 1 ) were also quite abundant. Coccinella abdomi- 
nalis was present in less abundance. Addlia flavomac- 
ulata DeG. (fig. 42), with its larvae, has been sent to 
the bureau as an enemy of Toxoptera in the Orange 
Free State, South Africa. 

Syrphid Flies. 

All through the Southwest in 1907 syrphids were very abundant 
and were an important factor in the control of Toxoptera. 

These insects are beautiful two-winged flies with prominent golden 
bands across the abdomen. They are always present in mild weather 
26675°— Bull. 110—12 9 





Fig. 39.— The nine-spotted lady-beetle 
{Coccinella 9-notata), an enemy of 
the spring grain-aphis: Adult. En- 
larged. (From Chittenden.) 



Fig. 40.— The nine- 
spotted lady-bee- 
tle (Coccinella 9- 
notala), an enemy 
of the spring grain- 
aphis: Larva. En- 
larged. (Fro m 
Chittenden.) 



130 



THE SPRING GRAIN-APHIS OR 



in grain fields badly infested with plant-lice, and when quite num- 
erous attract attention by a buzzing noise made while in flight. The 
predaceous larvae are sluglike and of a dirty grayish or yellowish 
green color ; this is the only stage in which they are destructive to 



^^6****^ 





Fig. 41. 



-The spotted lady-beetle (Megilla maculata), an enemy of the spring grain-aphis: a, Larva; b, 
empty pupa skin; c, adult. Enlarged. (From Chittenden.) 



plant-lice. Little is known of the life histories of these insects as 
very few careful rearings have been made. 

SyrpJius americanus Wied. (fig. 43) and Eupeodes volucris O. S. 
(fig. 44) were by far the most numerous syrphids in the grain fields in 

the Southwest in 1907. A field at 
Kingfisher, Okla., in April, 1907, 
literally swarmed with them; 20 
or more could be taken with each 
sweep of an insect net. A curious 
fact with reference to their occur- 
rence in such abundance in this 
field, however, was that Toxoptera 
was not present there in destruc- 
tive abundance, while the adjoin- 
ing field was suffering greatly from 
their attack, though, curiously 
enough, the syrphid flies did not 
appear to be so plentiful there. 
These two species were present, 
apparently, over the entire south- 
western area that suffered greatly from Toxoptera attack in 1907. 
SyrpJius americanus was reared also from Toxoptera material sent in by 
Mr. E. C. Haynsworth from Sumter, S. C. Prof. J. M. Aldrich states in 
his catalogue of North American Diptera that he reared Eupeodes 
volucris from Aphis avense at Moscow, Idaho. Dr. C. V. Riley states, 




Fig. 42.— A South African lady-beetle, Adaliaflavo- 
maculata, which with its larva attacks the spring 
grain-aphis in the Orange Free State, South 
Africa. Enlarged. (Original.) 



PREDACEOUS ENEMIES. 



131 



in a report of the Department of Agriculture, 1 that he reared Syrphus 
americanus from MacrosipTium granaria. 




Fig. 43.— Syrphus anuricanus, whose larva destroys the spring grain-aphis: a, Female fly; o, second 
abdominal segment of male. Enlarged. (Original.) 

Splixrophoria cylindrica Say (fig. 45) was collected from wheat 
fields at Hiawatha, Kans., in 1907, by the junior author and was also 




Fig. 44.— Eupeodcs volucris, whose larvse were the most abundant and useful in the fields where the spring 
grain-aphis was most abundant in the Southwest during the spring of 1907. a, Female fly; b, abdomen 
of male; c, hypopygium of male. Enlarged. (Original.) 

reared from Toxoptera material sent in by Mr. Haynsworth from 
Sumter, S. C, the same year. Mr. G. G. Ainslie reared it from 

i Report of the Entomologist, U. S. Dept. of Agr. for 1889, p. 351. 



132 



THE SPRING GRAIN-APHIS OR 



Toxoptera at Monetta, S. 0., in 1908. Dr. Riley states that he 
found the larvge feeding on Macrosiphum granaria. 

Mr. Ainslie took quite a number of Allograpta obliqua Say in the 
Southwest in 1907, and, though we can not say definitely that it 
feeds upon Toxoptera, the chances are that it does, as Dr. Riley 
states that it feeds upon Macrosiphum granaria. 

Mr. Kelly reared a number of Baccha clavata Fab. from Aphis 
setarise at Wellington, Kans., in 1908; Mr. R. A. Vickery also reared 
B. clavata from Aphis maidis at Brownsville, Tex., in 1911; Mr. J. J. 




Fig. 45. — Sphxroplioria cylindrica, a fly reared from larvae attacking trie spring grain-aphis in South Caro- 
lina in 1907: a, Female fly; 6, dorsal view of abdomen of male; c, hypopygium of male, lateral view. 
Enlarged. (Original.) 

Davis reared this species at Lafayette, Ind., from Aphis medicaginis, 
also in 1911. This species may in future be found to attack Toxop- 
tera also. 

Lace-Wing Flies. 

The lacewing fly Chrysopa plorabunda Fitch*was quite abundant 
in the grain fields in the Southwest in 1907 and without doubt 
assisted materially in the destruction of Toxoptera. This is the 
most common species in this section of the country, where it hiber- 
nates in the adult stage ; thus, whenever the weather becomes suitable 
it is ready to at once begin oviposition. An allied species is shown 
in figure 46. 

The larvae of these insects can move about quite freely and are 
provided with two long, curved mandibles (see fig. 46) upon which 



PREDACEOUS ENEMIES. 



133 



plant-lice or other insects are impaled and held prisoners until they 

are sucked dry. They are then released and the Chrysopa larvae 

hunt other victims. 

CecidomyiidfiB. 

During September of 1909, at Lafayette, Ind., a new predaceous 
insect enemy to Toxoptera was discovered in the larvae of a little 
cecidomyiid or two-winged fly, determined tentatively for us as 
Apliidoletes sp. by Dr. E. P. Felt. It was first observed in one of the 
stock cages and afterwards it was found to be reproducing in the fields 
on Myzus persicse. 




Fig. 4G.— The golden-eyed lace-wing fly ( Chrysopa oculata), an enemy of the spring grain-aphis, a, Eggs; 
6, full-grown larva; c, foot of same; d, larva devouring an insect; e, cocoon; /, adult insect; g, head of 
same; h, adult, natural size. All enlarged except h. (From Marlatt.) 

We have not as yet carefully studied the life history of Apliidoletes 
sp. The adult fly (fig. 47) is a frail little creature, about the size of 
the clover-seed midge, pale cream in color, and the abdomen has a 
pinkish tinge, due to the pink eggs within. The eggs resemble 
those of the Hessian fly very closely except that they are much 
smaller. The larvae (fig. 48), which are pinkish in color, descend to 
the ground when fully matured, and at or near the surface they spin a 
loose cocoon, to which particles of dirt and trash adhere. In a few days 
the adults issue. The time required for this little insect to complete 
the entire life cycle is apparently about 10 to 14 days. The species 
is not determinable further than the genus for the reason that only 
the female adults have been secured. 



134 

This little fellow goes about getting its meals in a very quiet, 
unobtrusive sort of way. It crawls quietly up among a number of 
Toxoptera and the first one it touches becomes its victim. It at- 
taches its mouthparts to some joint of the legs, usually at the artic- 
ulation of the femur and tibia, and sucks out the juices of the 
aphidid. With a compound miscroscope the blood can readily be seen 
flowing in a constant stream, through the limb of the aphidid attacked, 
into the larva of the cecidomyiid. Barely is the aphid disturbed 
and upon close observation the skin of the aphidid will be seen to 




Fig. 47.—Aphidoletcs sp., cecidomyiid fly whose larvae feed upon the spring grain-aphis. Greatly 

enlarged. (Original.) 

gradually shrivel up ; finally nothing but the empty skin remains and 
the larva crawls away in search of more aphidids, frequently with 
the old empty aphidid skin adhering to it. The time required to 
consume the juices of an aphidid varies with the size of the larva 
and of the aphidid. A larva that is about full grown can dispatch 
a small aphidid in a few minutes, while from 15 to 30 minutes are 
required for it to empty a full-grown one. These cecidomyiid larvae 
have enormous appetites and apparently keep up their work of 
destruction almost constantly until they become full grown. 

It is not at all impossible for this insect to become a very im- 
portant factor in the control of Toxoptera, as the adults are capable 
of flight and deposit large numbers of eggs. 






MISCELLANEOUS ENEMIES. 



135 




Birds. 

Birds devour immense numbers of the spring grain-aphis. Miss 
Margaret Morse, of Clark University, has been kind enough to conduct 
some experiments for us in feeding Toxoptera to quail. She has 
learned that they are very fond of the aphidids and estimates that 
about 5,000 individual Toxoptera were eaten by a single quail in one 
day, preference being shown for those that were unparasitized. 

Mr. W. L. McAtee, of the Biological Survey of the United States 
Department of Agriculture, made some special studies of the aphis- 
eating habits of some of our birds in March- April, 1909, at Winston- 
Salem, N. C, at the time Toxoptera was so destructive in that 
vicinity. He states that in a wheat field of about 
100 acres there were over 3,000 birds present 
daily; sometimes the number ran as high as 8,000 
to 9,000. So large a number of birds would be 
found in the fields only during migration, and 
even at that time the presence of so many indi- 
cates that they were attracted to the fields by 
the abundant food. In so far as could be ascer- 
tained, about nine-tenths of the birds were feed- 
ing upon aphidids (including Toxoptera graminum, 
Maerosiplium granaria, and Aphis avense), some 
taking as many as 180 at a single meal. These 
aphidids are very small, soft-bodied insects and 
many meals would be required by a bird in a 
single day to satisfy its hunger. The average 
number per meal was at least 50, and we may 
assume that 6 times this number were taken per 
day. On this basis the number of aphidids de- 
stroyed by birds on the farm daily during the 
migration season is 90,000. Below is a partial 
list of the species Mr. McAtee found devouring Toxoptera at 
Winston-Salem. A complete list can not be given at this time, 
since his studies are not yet finished; many species will undoubtedly 
be added. 

Goldfinch (Astragalinus tristis). 

Vesper sparrow (Pocecetes gramineas) . 

Savanna sparrow (Passerculus sandwichensis savanna). 

Chipping sparrow (Spizella socialis). 

Song sparrow (Melospiza melodia). 

All of these birds occur over the entire South. 

MISCELLANEOUS ENEMIES OF TOXOPTERA. 

Under the head of miscellaneous enemies may be considered ene- 
mies that are of very slight economic importance; those* in other 
words, that have been observed occasionally attacking Toxoptera. 



Fig. 4S.—Aphidoletes sp., 
cecidomyiid larva 
which attacks the 
spring grain-aphis, a 
Larva; b, anterior ex 
t r e m i t y protruded 
showing breastbone; c 
ventral view of poste 
rior segment, a, Much 
enlarged; b, c, greatly 
enlarged. (Original.) 



136 THE SEEING GRAIN-APHIS OE " GEEEN BUG. 



>> 



In 1890 the senior author, at Lafayette, Ind., found that the young 
of the snowy tree-cricket (CEcanthus niveus De G.) were very fond 
of Toxoptera and fed upon them freely. 

Mr. A. N. Caudell, of this bureau, observed one of the soldier bugs, 
Reduviolus ferus L., attacking Toxoptera on the grounds of the De- 
partment of Agriculture at Washington in 1908. During the same 
year Mr. C. N. Ainslie found a larva of a species of the ladybird genus 
Scymnus at Mesilla Park, N. Mex., attacking Toxoptera, and he 
seems to think that numbers are devoured by this insect. 

In 1909, at Washington, D. C, Mr. E. A. Vickery reared the 
braconid Lipolexis piceus Cress, in limited numbers from Toxoptera. 

The junior author has at times found a fungous disease attacking the 
aphidids in Ins rearing cages, but we have never noted this in the fields. 

ANTS AND THEIR RELATION TO TOXOPTERA. 

So far as our observations go Toxoptera is not so attractive to 
ants as are many other species of plant-lice. We have often found 
various species of ants in attendance on Toxoptera, but the relations 
did not appear to be mutually beneficial, the ants nearly always 
gaining the most by such partnerships. 

At Hooker, Okla., in 1907, the junior author found ant burrows 
beside plants in an area badly infested with Toxoptera. In this case 
some burrows were found where the aphidids were slightly below 
ground on plants in these burrows, the ants being busy about the 
aphidids, stroking them with their antennae. Mr. C. N. Ainslie many 
times observed ants stroking Toxoptera with their antennae. We have 
found no instances, however, in which ants care for the eggs of Toxop- 
tera in winter, and Toxoptera does not appear to excrete so much 
honey dew as do some other aphidids. This probably accounts for the 
fact that they are not so popular with the ants as are certain other 
aphidids. 

In Texas, during 1909, Mr. T. D. Urbahns found ants busily caring 
for Toxoptera in his rearing cages. He also noted that the ants al- 
ways attacked the parasite of Toxoptera (ApJiidius sp.) whenever 
they came in contact with it, tearing the larvae out of the old dead 
bodies of Toxoptera and destroying them. 

REMEDIAL AND PREVENTIVE MEASURES. 

With an outbreak of this pest fully established, and the winged 
adults being carried by the winds and scattered over the fields, there 
to settle down and reproduce, the difficulties in the way of control 
are quite insurmountable. 

FIELD EXPERIMENTS. 
The brush-drag experiments that were carried out under the direc- 
tion of the junior author at Hobart, Okla. (see Plate IX, fig. 1), have 
not, with the trials we have given the brush drag, proved satisfactory, 
although Mr. Thos. J. Anderson, Government entomologist of British 



Bui. 1 10, Bureau of Entomology, U. S. Dept. of Agriculture. 



Plate IX. 




Fig. 1.— Brush Drag Used by the Junior Author in Experiments and also by 
Farmers in Destroying the Spring Grain-Aphis in the Fields at Hobart, 
Okla. (Original.) 



1 ^ * <^l^ 


^g Ai-j^fJS* 





Fig. 2.— Roller Used in Experiments by Junior Author and by Farmers in 
Destroying the Spring Grain-Aphis in Oklahoma. (Original.) 



REMEDIAL AND PREVENTIVE MEASURES. 137 

East Africa, states that it is with them the most effective measure at 
their command for destroying the " green fly" in wheat fields. With 
us it was used after the aphidid had fully established itself and was 
literally swarming over the growing grain. Earlier, at the commence- 
ment of an outbreak, the effect of its use might prove more satisfactory. 

Similar experiments were carried out with a heavy roller, such as is 
generally used among farmers for crushing clods in fields and com- 
pacting the ground. (See PI. IX, fig. 2). In this case the results 
were even less satisfactory than with the brush drag, because the 
roller acted only on the clods and other inequalities in the surface of 
the ground. Where the wheat had been drilled the effect on the Tox- 
optera was less decisive than where the grain had been sown broad- 
cast. The wheat plants grow in the narrow furrows or grooves and 
the insects that were displaced dropped down about the plants and 
the passing roller struck only the ridges, leaving the insects practically 
untouched. 

Where the invasion is not chiefly from outside the field itself, and 
the pest makes its first appearance in spots, management is less 
difficult. By plowing under these infested spots and immediately 
harrowing and rolling them further damage may be effectually pre- 
vented. The junior author had an opportunity to test this measure 
in western Oklahoma. Covering these spots with straw, where easily 
obtainable, and burning, is equally effective, but where this last 
measure was applied by farmers in Oklahoma in 1907 the fields were 
so completely overrun from the outside that the good effects were 
entirely obliterated. 

As between these two methods of suppression, it must be borne in 
mind that while the seriously affected spots in a field are very small, 
a single load of straw will suffice to cover a number of them, prepara- 
tory to burning, but after these areas become enlarged it is much more 
practicable to plow them under. 

Besides the above-mentioned methods of control, experiments 
were conducted with different kinds of spray materials. In all of 
our control methods we endeavored to place ourselves in the position 
of the farmer, and to use such apparatus as could be obtained locally. 
Accordingly the junior author, upon reaching Hobart, Okla., the 
first week in April, 1907, prepared to begin some spraying experi- 
ments. The only spray apparatus that could be found in the town 
was a knapsack pump. As stated above, since an outbreak of 
Toxoptera starts in small areas, where the infestation originates 
within the field, it was thought possible to accomplish something by 
spraying these areas. As the infestation at Hobart seemed to be 
quite general, apparently originating from migrations from farther 
south and east, the small pump was found to be utterly useless. 
From here the junior author proceeded to Kingfisher, Okla., where 
there were clearly defined areas of infestation, and, together with 



138 THE SPUING GRAIN-APHIS OR 

Mr. C. N. Ainslie, began experiments with a barrel pump, loaned by a 
market gardener. One plat was sprayed with 5 per cent kerosene 
emulsion; another with 10 per cent kerosene emulsion; a third plat 
with ordinary hard soap, 1 pound to 4 gallons of water; a fourth plat 
with whale-oil soap, 1 pound to 6 gallons of water. The spraying 
was done carefully, so as to reach every aphis possible. Upon 
examination the next day it was found that the 10 per cent emulsion 
and the hard soap had injured the plants. Not more than 50 per 
cent of the plant-lice were killed in any of the experiments. On the 
15th of April the sprayings were repeated with similar results. All 
of the aphidids could not be reached, no matter how thoroughly 
the spraying was done. It was quite evident that unless the ground 
was almost soaked there would be little or no relief. These spray- 
ings cost at the rate of about $4 per acre. 

During the latter part of July it was found that Toxoptera was 
very abundant on the lawns of the Department of Agriculture at 
Washington, D. C. This outbreak became known to Mr. E. M. 
Byrnes, Superintendent of Experimental Gardens and Grounds, 
who at once had the entire infested block sprayed with a solution of 
one-half gill of blackleaf tobacco extract to each gallon of weak 
soapsuds. The application was, however, ineffective. Four days 
later a strip through this plat was thoroughly saturated with a 
strong solution of barnyard manure, made by soaking the manure 
in water. While there was no evidence that this lulled any of the 
" green bugs," after nine days the pest was visibly less on this area 
than where the application of manure solution was not made. 

A series of experiments was then undertaken under the senior 
author's direction by Mr. E. O. G. Kelly, as follows: 

TobacGO dust was applied at rates of one-fourth, one-half, and 
1 pound to each 100 square feet, but after over a week had elapsed 
from the date of application no effect was to be observed and no dead 
insects were found. 

Kerosene emulsion was applied at 8 and 10 per cent strengths, 
and at the end of nine days no " green bugs " were to be found on the 
areas so treated. Also there was no perceivable injury to the grass. 

Whale-oil soap solutions, varying in strength from one-fourth of 
a pound to 2 pounds of soap to each 5 gallons of water, were applied 
to similar s areas. In this case the stronger solution injured the 
grass slightly, but not permanently; in the case of the lesser strengths 
there was no injury to the grass whatever. The effect on the "green 
bug" was the same in every case. They were not only literally 
exterminated over the areas treated, but the applications seemed to 
protect from a reinfestation, in case of even the weakest solution. An 
examination five days after the application was made revealed the 
"green bugs" in myriads and breeding freely on the untreated space, 
while only 8 inches away and on the treated area living bugs were 



REMEDIAL AND PREVENTIVE MEASURES. 139 

scarcely to be found, although the dead bugs were to be observed 
almost as abundantly as were the living on the space untreated. 
It must be remembered, however, that these experiments were 
carried out in grass kept closely cropped by frequent use of the 
lawn mower, and such areas can be sprayed much more effectively 
than a wheat field, where the ground would have to be literally 
soaked in order to reach all of the aphidids. 

In the light of these experiments field spraying seems an impracti- 
cal measure, even when small areas are involved. Burning or plow- 
ing would probably be more effective and the recommendations 
would probably be more readily complied with, as the average farmer 
does not usually have spray pumps of any description. 

Lime and sulphur was dusted on the plants in badly infested areas 
with practically no benefits. 

CULTURAL METHODS. 

Examination of a large number of fields infested by Toxoptera, 
extending over a wide range of country, resulted in securing a con- 
siderable mass of information that may be included under the head of 
cultural methods. 

The senior author visited Sumter, S. C, April 17, 1907, driving 
over much of the country in that vicinity. All fields of fall-sown 
oats, the only grain grown, were infested, there being no perceivable 
difference in severity of attack between fields following cotton, 
those following oats, and those on new ground, thus showing that 
the pest had swept over the country, diffusing itself generally. 

At Winston-Salem, N. C, April 19-20, where both wheat and fall 
oats were grown, the ravages of the pest were much more serious, 
and fall-sown oats were completely ruined. A part of one field 
that had been in oats the previous year had, that fall, thrown up a 
heavy growth of volunteer grain, while the remaining portion was 
free of this growth. Wheat was drilled directly across both these 
areas on November 15, 1906, the whole field having first been pre- 
pared by disking, leaving much of this volunteer grain undisturbed. 
April 20, 1907, when examined by the senior author, the wheat on the 
part that had been overgrown with volunteer oats the previous 
fall was totally ruined, while on the clean part the damage was about 
50 per cent. In wheat fields generally there was a marked difference 
in severity of attack as between those seeded before and those sown 
after about November 1, 1906, the later-sown suffering little while 
that sown earlier, on ground where there was much volunteer wheat 
or oats, was seriously damaged. This indicated that the trouble 
had been aggravated by the volunteer growth at the time of wheat 
seeding the previous autumn. It was very significant that in late- 
sown fields on clean ground the injury was comparatively small. 

In Oklahoma it was observed by both the junior author and Mr. 
C. N. Ainslie that late-sown and pastured fields were destroyed much 



140 THE SPRING GRAIN-APHIS OR 

more quickly and completely than earlier sown, unpastured fields. 
But it must be remembered that here the almost universal destruc- 
tion was caused principally by Toxoptera drifting in from outside 
sources. 

One feature of attack by Toxoptera has been especially noticeable 
throughout most portions of the country seriously ravaged by the 
pest, particularly where only wingless viviparous females have been 
found. In such fields the destruction was confined to circular areas 
which constantly increased in size as the season advanced, so long as 
meteorological conditions favorable to the increase of the pest pre- 
vailed; unless, in the meantime, the entire field had become overrun 
from the swarms drifting in from without. The occurrence of these 
spots (see Plate I, fig. 2) in the fields, while general, is not universal. 
For instance, the senior author did not observe them in the fields of 
fall-sown oats in South Carolina, in April, 1907, but he did find them 
about Winston-Salem, N. C, a day or two later. At Summers, 
Ark., Mr. C. N. Ainslie, observed a field of wheat, March 18, 1907, 
where a rectangular strip at one end had been totally killed out by 
Toxoptera, and learned from the owner that this area exactly corre- 
sponded with that of a small patch of oats which the previous year 
had failed to produce more than a very poor crop and had been 
plowed under without cutting. In preparing the ground for wheat 
in the fall of 1906, a volunteer growth of oats was reported to have 
sprung up on this area after plowing. Again the same observer, a 
little later in the season, found that the regularity of the occurrence 
of these spots in rows across a field, in northern Oklahoma, exactly 
corresponded to the location in this same field the previous summer 
of oat shocks, which had been allowed to stand out through a period 
of wet weather; the volunteer grain having sprung up there later in 
the season and remained growing amongst the young wheat in the 
fall. In Texas the relation of this volunteer growth in the fields, 
in autumn and early winter, to the abundance of Toxoptera does not 
appear to differ materially from what is known to occur elsewhere. 
When the secretary of the Texas Grain Dealers' Association first 
appealed to the Government for aid in investigating the pest, particu- 
lar attention was directed to the possibility that methods might be 
devised for its control by spraying or otherwise treating the spots in 
grain fields, for the purpose of checking its ravages before these 
infested spots had increased in size and before the pest had spread 
from them over the entire field. 

Thus it will be seen that primarily infestation is first invited by 
the volunteer growth starting up in cultivated fields in autumn. 
If such fields are sown to wheat or oats in the fall, the pest spreads 
from this earlier growth to the younger and more tender grain. This 
will of itself suggest several entirely practical cultural methods likely to 
restrict and prevent the development of the pest in the fields in autumn. 



REMEDIAL AND PREVENTIVE MEASURES. 141 

Crop rotation could scarcely fail of giving beneficial results. ' The 
destruction of all volunteer grain springing up in fields from which 
grain has been removed at thrashing gives promise of the greatest 
relief. Indeed, if careful attention were given to all fields in autumn, 
and all of this volunteer growth were destroyed before any grain 
whatever was sown, it is doubtful if such serious ravages as have 
occurred in the past could be repeated. This can all be accomplished 
by close pasturing and careful late plowing, followed as soon as 
possible by seeding. 

At Hooker, Okla., the junior author found affected spots both on 
land that had been devoted to oats the previous year and on land that 
had previously grown cowpeas. This, as well as some other observa- 
tions made by other parties, indicates that some of the grasses will 
have the same effect in inviting attack as volunteer grain growing 
up in the fields in the fall. 

It is therefore most urgently recommended, and especially for the 
South, that all of this volunteer growth of whatever nature be com- 
pletely killed out in the fields before seeding the following crop. Not 
only will this mode of procedure benefit especially the southern 
grain grower, but in the light of our present knowledge of the pest, 
it will serve as a protection to the spring oats crop over a large area of 
country where it is doubtful if serious ravages would occur at all 
were there not myriads of the pest continually developing to the 
South and drifting northward in spring with the advance of the season. 

Following along the same line, attention should be directed to the 
probability that late seeding may prove a preventive of attack, for 
the reason that the pest will obviously gain less of a foothold in a 
late-sown field than it will where there has been an early growth of 
young grain plants. In other words, there is a likelihood that the 
pest may break out in spots, as has been several times previously 
noted, and to this extent late seeding is an advantage. However, 
this would be a serious disadvantage if the fields should afterward be 
overrun by hordes of migratory winged viviparous females in spring, 
for in this case the earlier sown and therefore the older and less succu- 
lent growth would suffer least from their attack. This is shown by 
the fact that late-sown and winter-pastured fields in Oklahoma 
suffered most in 1907. It must also be noted that at Winston-Salem, 
N. C, in April 1, 1907, wheat that had been sown about or a little 
prior to November 15, on ground free from young growth of volunteer 
grain, or the grasses, was practically uninfested even though located 
in the immediate vicinity of other badly infested fields sown earlier 
on ground more or less foul with young growth. All of this indicates 
pretty clearly that if all volunteer growth were eliminated in the fall, 
and the grain sown late, the pest would not 'become destructive. Of 
course the amount of benefit secured will depend upon the uniformity 
with which this method is carried into effect in any locality. 



142 THE SPRING GRAIN-APHIS OR ' GREEN BUG.' 

Over the northern part of the country where the insect passes the 
winter largely or wholly in the egg state, another measure can be 
applied to great advantage. The junior author has found that blue 
grass (Poa) is not only a summer food plant, but that it is very largely 
upon this grass that the eggs are deposited in the fall, and from 
which the offspring of the stem mothers make their way to the grain 
fields in spring. He has observed cases where the portion of a grain 
field bordered by bluegrass was the most seriously affected part of 
the entire field. If, then, roadsides, fence corners, and other waste 
lands were closely grazed in fall, winter, or early spring, these eggs 
would be largely destroyed and the food supply of the stem mother 
and her progeny cut off. This can always best be done during mild 
winters on account of a lack of snow. Where close pasturing is not 
practicable, burning over during the same season will have a similar 
if not an even more drastic effect. 

ARTIFICIAL INTRODUCTION OF PARASITES. 

As Apliidius testaceipes destroyed such hordes of Toxoptera in 
apparently very short periods of time, after they had once become 
established, we thought it possible materially to aid in this destruc- 
tion by introducing the parasites artifically into localities where they 
were apparently absent. As Mr. C. N. Ainslie was unable to find 
any evidence of parasitization in the fields about Wellington, Kans., 
on April 1, 1907, it was decided to begin operations there. Accord- 
ingly, on April 9, over a bushel of wheat leaves that were almost 
covered with parasitized Toxoptera were collected at Kingfisher, 
Okla. Mr. Ainslie took charge of this material, and on April 10, made 
a careful survey of the fields about Wellington, Kans., to determine 
the situation relative to Toxoptera infestation, and on the morning 
of April 1 1 he scattered a portion of this material in one of the most 
badly infested fields that could be found in that vicinity, the remain- 
der being left sheltered by the box lids. At this time he could find 
parasitized Toxoptera already in the fields, both the dead leathery 
bodies and those showing the characteristic yellow color. The 
parasites included in this introduction were roughly estimated at 
2,500,000; this number, however, was probably not a "drop in the 
bucket " to those already in the field. If there were only one or two para- 
sitized Toxoptera to a leaf, when a whole field is considered 2,500,000 
would seem to be a very small number. So far as published records 
show this was the first artificial introduction of parasites into Kansas. 

April 12 another lot of parasitized material, sent Mr. Ainslie by 
the junior author from Kingfisher, which was fully as large as the 
previous consignment, was introduced into another field 2 miles 
from the first. All of this material, originally intended for one field, 
was reported as one experiment by the junior author and appeared 
as one experiment in Circular 93, since Mr. AinshVs notes were not 
on file in the office at the time. We find, however, that Mr. Ainslie, 



ARTIFICIAL INTRODUCTION OF PARASITES. 143 

on his own initiative, conducted two separate experiments, thus 
rendering the results twice as valuable. 

April 18 a minor introduction of parasites was made at McPherson, 
Kans;, and on April 21 there was another similar one at Sterling, 
Kans. Parasitized "green bugs " were observed present at each place 
on these dates. 

Mr. Ainslie remained in the vicinity of Wellington, and more briefly 
at McPherson and Sterling, for the purpose of making accurate obser- 
vations on the effect of these introductions. 

Two weeks later, on visiting the two fields at Wellington, where 
the first introduction had been made, Mr. Ainslie found that on 
account of the cold weather the effect upon the parasites was almost 
the same as though they had been kept in cold storage. Some of 
those sheltered by the box lids had issued, but had apparently not 
ventured far from their shelter and were found in a semitorpid condi- 
tion capable of little movement. The percentage of parasitism from 
Aphidius appeared to be the same in all other fields in this locality, 
irrespective of these introductions, except close about the box lids, 
where they seemed a little more numerous, the conditions of para- 
sitization generally being about the same as had existed two weeks 
previous. The Toxoptera, however, had greatly increased in num- 
bers, and the fields were now plainly showing the effects of their work. 

Subsequent examinations of fields at Wellington showed that after 
the weather warmed up in May the parasites speedily overcame the 
Toxoptera and that the fields where these artificial introductions 
were made had suffered as much as any fields in the neighborhood 
from attack by the "green bug." All of this seems to indicate that 
no noticeable good resulted from these introductions, which, in the 
light of our present knowledge, is not at all surprising. The minor 
experiment at McPherson was also reported upon to us by Mr. W. 
Knaus, and his report was in accord with our own observations. 

On May 17 an artificial introduction of parasites was begun at 
Manhattan, Kans. 1 While this experiment bore out our former 
observations, the results obtained here should not bear as much 
weight as the earlier introductions, since the Toxoptera was already 
nearly overcome when the introduction was begun. 

When one stops to consider the numerous and varied hosts of 
Aphidius testaceipes, its manner of hibernation, its wide distribution, 
and the higher temperature required for its development over and 
above that needed by its host ; also the fact that it may readily be 
transported along with its host as adults, or within the body of the 
latter, one can readily see the futility of attempting materially to 
increase its numbers or efficiency by artificial introduction into 
grain fields. 

i Cir. 93, Bur. Ent. U. S. Dept. Agr., pp. 10-12, Aug. 22, 1907; Cir. 93, revised, Bur. Ent., U. S. Dept. 
Agr., pp. 12-13, June 23, 1909. 



144 THE SPRING GRAIN-APHIS OR ' ' GREEN BUG. ' ' 

LITERATURE CONSULTED. 

Aldrich, J. M. — Catalogue of North American Diptera. 

Aldrich, J. M. — Cultivator and Country Gentleman, vol. 47. p. 498, June, 1882. 

Ashmead, Wm. H.— Proc. U. S. Nat. Mus., vol. 11, 1888. 

Biro, Lajos. — Rovartani Lapok, vol. 2, p. 127, 1885. 

Buckton, G. B. — British Aphides, vol. 1, p. 80. 

Buckton, G. B. — British Aphides, rol. 3, pp. 135-136. 

Del Guercio, Giac. — Nuove relazioni ai lavori della R. Stazione di Entom. Agraria 

di Firenze, ser. 1, no. 2, pp. 144-145, 1900. 
Hegner, R. W.— Biol. Bui., vol. 16, no. 1, pp. 19-26, 1908. 
Hegner, R. W.— Journ. Morph., vol. 20, pp. 231-296, 1909. 
Horvath, G. — Rovartani Lapok, vol. 1, p. 143, 1884. 

Horvath, G. — Fauna Regina Hungarie, vol. 3 (Insecta Hemiptera), p. 60, 1897. 
Howard, L. O.— Ent. News, vol. 19, no. 8, pp. 365-367, 1908. 

Hunter, S. J. — The green bug and its enemies, Bui. Univ. Kans., vol. 9, no. 2, 1909. 
Huxley, T. H.— Trans. Linn. Soc, vol. 22, pt. 3, p. 215, 1858. 
Kelly, E. O. G.— Proc. Ent. Soc. Wash., vol. 10, nos. 3-4, pp. 163-164, 1908. 
Kelly, E. O. G.— Proc. Ent. Soc. Wash., vol. 11, pp. 64-66, 1909. 
Lecaillon, A. — Contribution a l'etude des premiers phenomenes d.u developpe- 

ment embryonnaire chez les insectes, parti culierment chez les Coleopteres. Archives 

D'Anatomie Microscopique, tome 1, 1897. 
Lecaillon, A. — Recherches sur le developpement embryonnaire de quelques 

Chrysomelides. Archives D'Anatomie Microscopique, tome 2, 1898. 
Macchiati, Luigi.— Bol. Soc. Ent. Ital., vol. 14, p. 246, 1882. 
Manns, Thos. F.— Bui. 210, Ohio Agr. Exp. Sta., 1909. 

Maxwell-Lefroy, H. — Agricultural Journal of India, vol. 3, pt. 3, pp. 243-244, 1908. 
Mazzanti, Dr. Dom Luigi. — Nuov. Ann. Sci. Nat. Bologna, ser. 3, vol. 6, pp. 342- 

352, 1852. 
Passerini, Giovanni. — Gli afidi (pamphlet), p. 25, 1860. 
Pergande, Theo.— Bui.. 38, Div. Ent., U. S. Dept. Agr., pp. 7-19, 1902. 
Phillips, W. J.— Proc. Ent. Soc. Wash., vol. 10, nos. 1-2, pp. 11-13, 1908. 
Riley, C. V.— Rept. U. S. Dept. Agr. for 1889. 

Riley, C. V., and Howard, L. O.— Insect Life, vol. 3, pp. 73-76, 1890. 
Rondani, Camillo. — Nuov. Ann. Sci. Nat. Bologna, ser. 2, vols. 8, 9, 1847. 
Rondani, Camillo. — Nuov. Ann. Sci. Nat. Bologna, ser. 3, vol. 6 (2), pp. 9-12, 1852. 
Sajo, Karl. — Zeitschr. f. Pnanzenkrankheiten, vol. 4, p. 4, 1894. 
Sajo, Karl.— Prometheus, vol. 1, 1889 (1890). 
Schouteden, H.— Mem. Soc. Ent. Belg., vol. 12, p. 231, 1906. 
Setterman, G. W.— Colman's Rural World, vol. 53, p. 193, 1890. 
Stahl, J. M.— Country Gentleman, vol. 55, p. 639, 1890. 
Tannreuther, G. W. — History of the germ cells and early embryology of certain 

aphids. Zoologische Jahrbucher, Band 24, Heft 4, 1907. 
Washburn, F. L— Can. Ent., vol. 40, pp. 53-54, February, 1908. 
Washburn, F. L. — Special Report of the State Entomologist of Minnesota, March 1, 

1908. 
Washburn, F. L.— Weather Crop Bui. Mo. State Bd. Agr., 1890. 
Webster, F. M.— Insect Life, vol. 4, pp. 245-248, 1892. 
Webster, F. M.— Cir. 93, Bur. Ent., U. S. Dept. Agr., 1907. 
Webster, F. M— Cir. 93, revised, Bur. Ent., U. S. Dept. Agr., 1909. 
Webster, F. M.— Proc. Ent. Soc. Wash., vol. 9, pp. 110-114, 1907. 
Webster, F. M.— Ann. Ent. Soc. Amer., vol. 2, no. 2, pp. 67-87, 1909, 
Weed, C. M.— Ohio Farmer, vol. 78, no. 3, p. 33, July 19, 1890. 
White, Gilbert. — Natural history and antiquities of Selbourne, pp. 365-366, 1836. 
Will, Ludwig. — Entwicklungsgeschichte der viviparen Aphiden. Zool. Jahrb. 

Abth. f. Anat., Bd. 3, pp. 201-286, 1888. 
Witlaczil, Em. — Entwicklungsgeschichte der Aphiden. Zeitschr. f. Wiss. Zool., 

Bd. 40, 1884. 



INDEX. 



Page. 

Abutilon, food plant of Macrosiphum sp 117, 125 

Adalia fiavomaculata, enemy of spring grain-aphis 18, 129 

Agropyron occidentale, food plant of spring grain-aphis in America 32, 41, 42, 43 

rcpens, food plant of spring grain-aphis in America 42, 43 

Europe 41,43 

tcncrum, food plant of spring grain-aphis in America 42, 43 

Alfalfa. (See Mcdicago sativa.) 

Allograpta obliqua, enemy of Macrosiphum granaria 132 

probable enemy of spring grain-aphis 132 

Allotria sp . , hosts 128 

in bluegrass infested by spring grain-aphis at Washington, D.C. . 37 

secondary parasite of spring grain-aphis 128 

Alopecurus gcniculatus, food plant of spring .grain-aphis in America 41, 43 

Ampclopsis sp. , food plant of aphidid 116, 125 

Andropogon hirtas, food plant of Toxoptera graminum in Africa 43 

A ndropogon sp . (See Sorghum . ) 

Ants, enemies of Aphidius sp 136 

spring grain-aphis 136 

Aphelinus mali, hosts 122, 125 

parasite of spring grain-aphis 103, 122-123, 125 

nigritus, life history and habits, notes 124 

parasite of Aphis setarix 125 

spring grain-aphis 103, 122, 123, 124, 125 

semifiavus, hosts 125 

parasite of spring grain-aphis 103 

sp. , probable host of Aphidencyrtas aphidiphagus 126 

Pachyneuron sp 127 

Aphidencyrtus aphidiphagus, hosts 126-127 

secondary parasite of spring grain-aphis 126-127 

Aphidid on Ampelopsis sp. , host of Aphidius testaceipes 116, 125 

Baccharis viminalis, host of Aphidius testaceipes. 117, 125 

bluegrass, host of Aphelinus semifiavus 123 

Capsella sp. , host of Aphidms testaceipes 116 

Chenopodium album, host of Aphidius testaceipes 116 

Eragrostis sp. , host of Aphidius testaceipes 117, 125 

Kochia scoparia, host of Aphidius testaceipes 116 

sp., host of Aphidius testaceipes 125 

locust, host of Aphidius testaceipes 116, 125 

Panicum sp. , host of Aphelinus mali 123 

peach, host of Aphidius testaceipes 125 

pigweed (?), host of Aphidius testaceipes 125 

plum, host of Aphidius testaceipes *. . . 116, 125 

Aphidius avenaphis, parasite of Macrosiphum cranaria 125 

spring grain-aphis ." 103, 122 

26675°— Bull. 110—12 10 « 145 



146 THE SPRING GRAIN-APHIS OR 

Page. 

Aphidius confusus, parasite of Macrosiphum erigeronensis 125 

spring grain-aphis 103, 122 

sp., parasite of spring grain-aphis 18 

prey of ants 136 

probable host of Allotria sp 128 

Aphidencyrtus aphidiphagus 126 

Megorismus sp 126 

Pachyneuron sp 127 

testaceipes, artificial introduction against spring grain-aphis, futility. 142-143 

description 104-105 

dispersion, effect of wet weather thereon 121 

influence of winds thereon 118-119 

effect of parasitism upon development of host 106-107 

fecundity of host 107-109 

fecundity 113-114 

hibernation 117-118 

hosts 115-117, 125 

identity 104-105 

larva, movement within host and manner of attaching it 

to plant 109-113 

life history 105-118 

oviposition 105-106 

parasite of spring grain-aphis 40, 103, 104-121 

parthenogenesis • 114-115 

period from egg to adult 106 

synonyms 104 

temperature influences 119-121 

undescribed species, parasite of Toxoptera graminum in Africa 122 

Aphidoletes sp., enemy of Myzus persicx 133 

spring grain-aphis 133-134 

Aphis avenx, Allotria sp. a secondary parasite 128 

host of Aphidius testaceipes 116, 117, 125 

prey of birds 135 

Eupeodes volucris 130 

brassicx, Allotria sp. a secondary parasite 128 

Aphidencyrtus aphidiphagus a secondary parasite 127 

host of Aphelinus radii 123, 125 

Aphidius other than Aphidius testaceipes 116 

Megorismus sp. a secondary parasite 126 

currant. (See Myzus ribis.) 

gossypii, Allotria sp. a secondary parasite 128 

host of Aphidius testaceipes . ..* 116, 117, 125 

Pachyneuron sp. a secondary parasite 127 

(?), host of Aphelinus semiflavus 125 

graminum= Toxoptera graminum 16 

maidi-radicis, host of Aphidius testaceipes 125 

males, females, and eggs in North Carolina 47 

maidis, host of Aphelinus semiflavus 125 

Aphidius testaceipes 116, 125 

Pachyneuron sp. a secondary parasite 127 

prey of Baccha clavata 132 

medicaginis, host of Aphidius testaceipes 116, 125 

prey of Baccha clavata 132 



INDEX. 147 

Page. 

Aphis middletoni, host of Aphidius testaccipes 116 

monardx, host of Aphelinus mali 123, 125 

cenotherx, host of Aphidius testaccipes 116, 125 

* on peach, host of Aphidius testaceipcs 117 

rum ids, host of Aphidius testaceipcs 116, 125 

sacchari (?), host of Aphelinus mali 123, 125 

sctarix, host of Aphelinus mali 122, 125 

nigritus 123, 125 

Aphidius testaccipes 116, 125 

P achy neuron sp., a secondary parasite 127 

prey of Baccha clavata 132 

sp., host of Aphidius testaccipes 125 

viticola. (See Macrosiphum viticola.) 

Arrhenathcrum clatius, food plant of spring grain-aphis in Europe 41, 43 

Astragalinus tristis, enemy of spring grain-aphis 135 

Audibertia stochoides, food plant of Macrosiphum sp 117 

Arena barbata, food plant of spring grain-aphis in Europe 41, 43 

clatior=Arrhcnatherum clatius 41, 43 

fatua, food plant of spring grain-aphis in Europe 41, 43 

sativa. (See Oats.) 

Baccha clavata, enemy of Aphis maidis 132 

medicaginis 132 

setarix 132 

Baccharis viminalis, food plant of aphidid 117, 125 

Barley, food plant of spring grain-aphis in America 43 

Europe 41,43 

1 ' Bermuda grass, ' ' food plant of spring grain-aphis in Africa 43 

Birds, enemies of Aphis avenx 135 

Macrosiphum granaria 135 

spring grain-aphis 135 

Black gum. (See Nyssa sylvatica.) 
Bluegrass (see also Poa pratensis). 

food plant of Rhopalosiphum pox 123 

African. (See Andropogon hirtus.) 

Bromus commutatus, food plant of spring grain-aphis in America 42, 43 

erectus, food plant of spring grain-aphis in Europe 41, 43 

hordeaceus, food plant of spring grain-aphis in Europe 41, 43 

inermis, food plant of spring grain-aphis in America 42, 43 

maximus= Bromus villosus 41, 43 

mollis=Bromus hordeaceus 41, 43 

porteri, food plant of spring grain-aphis in America 42, 43 

secalinus, food plant of spring grain-aphis in America 41, 42, 43 

tectorum (?), food plant of spring grain-aphis in America 42, 43 

unioloides, food plant of spring grain-aphis in America 42, 43 

villosus, food plant of spring grain-aphis in Europe 41, 43 

Brush drag against spring grain-aphis 136-137 

Buckwheat. (See Fagopyrum esculentum.) 

Burning-over infested spots against spring grain-aphis 137 

pastures against spring grain-aphis 142 

Capriola dactylon, food plant of spring grain-aphis in America 42, 43 

Europe 43 

Capsella bursa-pastoris, food plant of aphidid 116, 125 

Cecidomyiidse, enemies of spring grain-aphis 133-134 



148 

Page. 

Chsetochloa italica, food plant of spring grain-aphis in America 42, 43 

viridis, food plant of spring grain-aphis in America 42, 43 

Chaitophorus sp. , host of Aphidius testaceipes 116 

Megorismus sp. a secondary parasite 126 

Pachyneuron sp. a secondary parasite ' 128 

viminalis, host of Aphelinus semiflavus 123, 125 

Cheat. (See Bromus secalinus.) 

Chenopodium album, food plant of aphidid 116 

Chess, soft. (See Bromus hordeaceus.) 

Chrysopa plorabunda, enemy of spring grain-aphis 132-133 

Coccinella abdominalis, enemy of spring grain-aphis 129 

9-notata, enemy of spring grain-aphis 129 

Colopha eragrostidis, host of Aphelinus mali 123, 125 

Corn, food plant of spring grain-aphis in America 41, 43 

Europe 41, 43 

Couch grass. (See Agropyron repens.) 
Cricket, snowy tree. (See (Ecanthus niveus.) 

Crop rotation against spring grain-aphis 141 

Cultural methods against spring grain-aphis 139-142 

Currant, food plant of Myzus ribis 125 

Cynodon dactylon. (See Capriola dactylon.) 

Dactylis glomerata, food plant of spring grain-aphis in America 41, 42, 43 

Europe 41, 43 

Distichlis spicata, food plant of spring grain-aphis in America 42, 43 

Drag. (See Brush drag.) 

Echinochloa crus-galli, food plant of spring grain-aphis in America 42, 43 

Eleusine indica, food plant of spring grain-aphis in America 42, 43 

Elymus canadensis, food plant of spring grain-aphis in America 41, 42, 43 

striatus, food plant of spring grain-aphis in America 42, 43 

virginicus, food plant of spring grain-aphis in America 42, 43 

Eragrostis megastachya, food plant of spring grain-aphis in America 42, 43 

pilosa, food plant of spring grain-aphis in America 42, 43 

sp., Aphidius testaceipes swept therefrom 117 

food plant of aphidid 117, 125 

Eupeodes volucris, enemy of Aphis avenx 130 

spring grain-aphis 130 

Fagopyrum esculentum, food plant of spring grain-aphis in Europe 41, 43 

Fescue, hard. (See Festuca duriuscula.) 
meadow. (See Festuca elatior.) 
sheep's. (See Festuca ovina.) 
various-leaved. (See Festuca heterophylla.) 

Festuca duriuscula, food plant of spring grain-aphis 42, 43 

elatior, food plant of spring grain-aphis in America 42, 43 

heterophylla, food plant of spring grain-aphis in America 43 

ovina, food plant of spring grain-aphis in America 42, 43 

rubra, food plant of spring grain-aphis in America 43 

Fungous disease of spring grain-aphis 136 

Grass, Bermuda. (See Capriola dactylon.) 
blue. (See Poa pratensis.) 
couch. (See Agropyron repens.) 
Italian rye. (See Lolium multijlorum.) 
Johnson. (See Sorghum halepense.) 
rye. (See Elymus canadensis.) 



INDEX, 149 

Page. 
Goldfinch. (See Astragalinus tristis.) 
Grain-aphis, spring (see also Toxoptera graminum) . 

aberrant individuals 81 

age at which females begin reproducing 70-71 

ant enemies 136 

attack, character 44 

bird enemies 135 

birth of young 63 

confusion with Macrosiphum granaria 13, 23 

description of different instars 58-59 

summer forms 59-61 

diffusion, influence of temperature thereon 88-94 

winds thereon 81 

distribution in the eastern hemisphere 16-18 

western hemisphere 18-19 

earliest observations in America 13-16 

early records in Europe 16 

egg, description 95-97 

embryology 94-103 

observations 97-102 

summary 102-103 

enemies 103-136 

miscellaneous 135-136 

fecundity of oviparous forms 81 

viviparous female 73-75 

wingless versus winged females 75-76 

first generation, fifth instar or adult stem mother, descrip- 
tion 58-59 

first instar, description 58 

fourth instar, description 58 

second instar, description 58 

third instar, description 58 

food plants 41-43 

fungous enemy 136 

generations, number 52-57 

per year 63-70 

literature consulted 144 

longevity 72 

of sexes 80 

losses from depredations in 1907 39-40 

methods and material for embryological studies '. . . 95 

migratory female, description 60 

molting 61-62, 78 

number of generations per year 63-70 

molts 61-62 

oviparous development 78-81 

female, description 77-78 

forms, fecundity 81 

oviposition, age begun by females 78-79 

period 79-80 

place * 79 

outbreak of 1890 19-24 

1901 24 



150 THE SPRING GRAIN-APHIS OR " GREEN BUG." 

Page. 

Grain-aphis, spring, outbreak of 1903 24-26 

1907 27-38 

parasites, primary or true 104-125 

secondary. 125-128 

predaceous enemies 128-136 

preventive and remedial measures .*. 136-143 

pupae, measurements of antennal joints 61 

rearing methods 51-57 

remedial and preventive measures 136-143 

remedies, artificial introduction of parasites 142-143 

cultural methods 139-142 

field experiments 136-139 

treatment of affected spots 140, 141 

reproduction, age when begun by females 70-71 

reproductive period 71-72 

sexual forms 76-78 

descriptions 77-78 

situation in 1911 40 

stem mothers 58 

summer forms, first instar, description 59 

fourth instar, description 59 

second instar, description 59 

third instar, description 59 

viviparous development 44-78 

in the North 49-50 

South 44-49 

female, fecundity 73-75 

winged male, description 78 

viviparous female, measurements of antennal 

joints 61 

wingless female, description 60, 61 

versus winged females, fecundity 75-76 

young produced daily, average number 76 

Grazing, close, against spring grain-aphis 142 

' ' Green bug . " (See Grain-aphis , spring . ) 
Gum, black. (See Nyssa sylvatica.) 

Harrowing infested spots against spring grain-aphis 137 

Hippodamia convergens, enemy of spring grain-aphis 129 

Holcus halpensis, food plant of spring grain-aphis in America = . 43 

Hordeum csespitosum, food plant of spring grain-aphis in America 42, 43 

jubatum, food plant of spring grain-aphis in America 42, 43 

murinum, food plant of spring grain-aphis in America 42, 43 

Europe 41, 43 

nodosum, food plant of spring grain-aphis in America 42, 43 

pusillum, food plant of spring grain-aphis in America 41, 42, 43 

vulgar e. (See Barley.) 

Hosackia glabra, food plant of Myzus sp 117, 125 

Hyalopterus dactylidis, Allotria sp. a secondary parasite 128 

Megorismus sp. a secondary parasite 126 

Juncus tenuis, food plant of spring grain-aphis in America 42, 43 

Kerosene emulsion against spring grain-aphis 138 

Kochia scoparia, food plant of aphidid 116 

sp., food plant of aphidid 125 



INDEX. 151 

Fage. 

Lacewing flies, enemies of spring grain-aphis 132-133 

Ladybeetle, convergent. (See Hippodamia convergens .) 
nine-spotted. (See Coccinella 9-notata.) 
spotted. (See Megilla maculata.) 

Ladybeetles, enemies of spring grain-aphis 128-129 

Lime and sulphur against spring grain-aphis 139 

Lipolexis piceus, parasite of spring grain-aphis 136 

Locust, food plant of aphidid 110, 125 

Lolium multifiorum, food plant of spring grain-aphis in America 43 

perenne, food plant of spring grain-aphis in F.urope 41. 43 

Lysiphlebus abutilaphidi*= Aphidius testaceipes 104 

baccJuiraphidis= Aph id 7 us testaceipes 104 

basilar is —Aphidius testaceipes ]04 

citraphis= Aphidius testaceipes -. 104 

coquilletti (?)=Aphidius testaceipes ]04 

crawfordi= Aphidius testaceipes ]04 

cucurbitaphidis= Aphidius testaceipes 104 

eragrostaphidis= Aphidius testaceipes 104 

gossypii= Aphidius testaceipes 104 

minutus= Aphidius testaceipes 104 

myzi= Aphidius testaceipes . 104 

persiaphidis= Aphidius testaceipes 104 

persicaphidis= Aphidius testaceipes . - . . 104 

piceiventris= Aphidius testaceipes 104 

tritici= Aphidius testaceipes 37, 104 

Macrosiphum cucurbitae, host of Aphidius testaceipes 117, 125 

erigeronensis, Pachy neuron sp. a secondary parasite 127 

granaria, host of Aphidius avenaphis 125 

testaceipes 116, 125 

in North and South Carolina in 1907 36 

males and oviparous females in rearing cages in Texas . . 47 

Pachyneuron sp. a secondary parasite 127 

prey of Allograpta obliqua 132 

birds 135 

Sphserophoria cylindrica 131-132 

Syrphus americanus 131 

spring grain-aphis mistaken therefor 13, 23 

pisi, Megorismus sp. a secondary parasite 126 

rosse, host of Aphelinus mali 123, 125 

sp. on Abutilon, host of Aphidius testaceipes 125 

black gum {Nyssa sylvatica), host of Aphidius testaceipes. 116, 125 

riticola, Allotria sp. a secondary parasite 128 

host of Aphidius testaceipes 116, 125 

Pachyneuron sp. a secondary parasite 127, 128 

"Manure against spring grain-aphis 138 

Medicago sativa, food plant of spring grain-aphis in America 42, 43 

Megilla maculata, enemy of spring grain-aphis 129 

Megorismus sp., hosts 125-126 

secondary parasite of spring grain-aphis 125-126 

Melanoxantherium sp., host of Aphidius testaceipes 116, 125 

Melospiza melodia, enemy of spring grain -aphis .* 135 

Millet. (See Chaetochloa italica.) 

Japanese. (See Echinochloa crus-galli.) 



152 

Page. 

Myzus mahaleb, host of Aphelinus mali 125 

persicse, Allotria sp. a secondary parasite 128 

host of Aphelinus semijiavus 123, 125 

Megorismus sp. a secondary parasite 126 

prey of Aphidoletes sp 133-134 

ribis, host of Aphidius testaceipes 117. 125 

sp. on Hosaclia glabra, host of Aphidius testaceipes 117, 125 

Nyssa sylvatica, food plant of Macrosiphum sp . 116 

Oats, food plant of spring grain-aphis in America 41, 43 

Europe 41, 43 

(Ecanthus niveus, enemy of spring grain-aphis 136 

Oryza saliva. (See Rice.) 

Pachyneuron sp. hosts 127-128 

probable parasite of Aphelinus sp 127 

secondary parasite of spring grain-aphis 127-128 

Panicum sp. food plant of aphidid : 123 

Parasites of spring grain-aphis, artificial introduction 142-143 

Passerculus sandwichensis savanna, enemy of spring grain-aphis 135 

Pasturing. (See Grazing.) 

Peach, food plant of aphidid 125 

Pemphigus fraxinifolii, host of Aphelinus mali 123, 125 

Pigweed. (See Chenopodium album.) 

(?), food plant of aphidid 125 

Plowing-under infested spots against spring grain-aphis 137 

Plum, food plant of aphidid 116, 125 

Poa annua, food plant of spring grain-aphis in Europe . . 41, 43 

compressa, food plant of spring grain-aphis in America 42, 43 

pratensis (see also Bluegrass). 

food plant of spring grain-aphis in America 42, 43 

Polypogon montspeliensis, food plant of spring grain-aphis in America 42, 43 

Pooecetes gramineus, enemy of spring grain-aphis 135 

Quail, enemy of spring grain-aphis 135 

Rains, protracted, effects on diffusion of Aphidius testaceipes 121 

Reduviolus ferus, enemy of spring grain-aphis 136 

Rhopalosiphum pose,, probable host of Aphelinus semijiavus 123 

Rice, food plant of spring grain-aphis in America 42, 43 

Europe 41, 43 

Rolling against spring-aphis 137 

Rye, food plant of spring grain-aphis in America 41, 43 

Schizoneura americana, host of Aphelinus mali 122, 125 

Pachyneuron sp. a secondary parasite 128 

lanigera, host of Aphelinus mali 122, 123, 125 

Scymnus sp., enemy of spring grain-aphis 136 

Seeding, late, against spring grain-aphis 141 

Siphocoryne avense should probably be called Aphis avenx 47 

Siphonophora avenae= Macrosiphum granaria 13, 23 

sp. on Abutilon, host of Aphidius testaceipes 117 

Audibertia stochoides, host of Aphidius testaceipes .....' 117 

Soap against spring grain-aphis 138 

whale-oil, against spring grain-aphis 138-139 

Sorghum, food plant of spring grain-aphis in America , . - 43 

Europe 41, 43 

halepense, food plant of spring grain-aphis 42 



INDEX. 153 

Page. 
Sparrow, chipping. (See Spizella socialis.) 

savanna. (See Passerculus sandwichensis savanna.) 
song. (See Melospiza melodia.) 
vesper. (See Pooecetes gramineus.) 

Spelt, food plant of spring grain-aphis in America 43 

Europe 41, 43 

Sphxrophoria cylindrica, enemy of Macrosiphum granaria 131-132 

spring grain-aphis 131 

Spizella socialis, enemy of spring grain-aphis 135 

Sporobolus neglectus, food plant of spring grain-aphis in America 42, 43 

Spraying experiments against spring grain-aphis 137-139 

Stipa leucotricha, food plant of spring grain-aphis in America 42, 43 

viridula, food plant of spring grain-aphis in America 42, 43 

Sulphur and lime against spring grain-aphis 139 

Syrphid flies, enemies of spring grain-aphis , 129-133 

Syrph us amcricanus, enemy of Macrosiphum granaria 131 

spring grain-aphis 130 

Temperature, influence on diffusion of spring grain-aphis 88-94 

influences on Aphidius testaceipes 119-121 

in relation to development of spring grain-aphis in North 49-50 

South 44-49 

outbreak of spring grain-aphis in 1907 28-29 

Tetraneura colophoidea (?), host of Aphelinus mali 123, 125 

"Texas louse," early name for spring grain-aphis 22 

Tobacco dust against spring grain-aphis 138 

extract against spring grain-aphis 138 

Toxoptera graminum (see also Grain-aphis, spring). 

parasites and their hosts 125 

Triticum repens. (See Agropyron repens.) 
spelta. (See Spelt.) 

villosum, food plant of spring grain-aphis in Europe 41-43 

vulgare. (See Wheat.) 

Volunteer growth of grain in relation to outbreaks of spring grain-aphis 140, 141 

Weather, wet, effect on diffusion of Aphidius testaceipes 121 

Wheat, food plant of spring grain-aphis in America 41, 43 

Europe 41, 43 

Winds, influence on dispersion of Aphidius testaceipes. ..".... 118-119 

spring grain-aphis 81-88 

Zea mays. (See Corn.) 

o 



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